VBA help for engineering project

Though I would ask the wise here for help.
Trying to explain what i am trying to do would take a while (and i am not 100% sure my self, it is from a handout) But i run this macro, it does not do anything.

Short cut crtl+I creates a matrix of initial internal temperature values for a section of a cylinder
crtl+e creates a matrix of external temperatures
crtl+c calculates run the third sub to calculate the non capacitance heat transfer thingy me bob. All is grand, stepping through it gives me no more errors.

I suppose the question is in the end loop bit, what is the correct way to write a loop as tnow and tmax do not seem to be working for me. What am i doing wrong?

Finde the whole file attached also.
Code:

[PHP]Sub Tstarti()
'Initial Internal Temp'
Dim Tstart As Single
Ti = Range("B4").Value

Dim outputregion As Range
'Tstart = Range("B14").Value
Tstart = Ti

Set outputregion = Range("C18:L28")

Dim arr(10, 10) As Single
For r = 1 To 10
For c = 1 To 10
arr(r, c) = Tstart

outputregion.Cells(r, c).Value = arr(r, c)
Next c
Next r

End Sub

Sub Tstarte()
'Initial External Temp'
Dim Tstart As Single
Te = Range("B5").Value

Dim outputregion As Range
'Tstart = Range("B14").Value
Tstart = Te

Set outputregion = Range("B18:B27")

Dim arr(10, 1) As Single
For r = 1 To 10
For c = 1 To 1
arr(r, c) = Te

outputregion.Cells(r, c).Value = arr(r, c)
Next c
Next r



End Sub




Sub nodes()

Const Nr = 10
Const Ny = 10

'dimensions

ReDim r(Nr), y(Ny), ra(Nr, Ny), yA(Nr), dV(Nr, Ny), Told(Nr, Ny), Tnew(Nr, Ny), arr(Nr, Ny) As Single
ReDim rALocation(Nr), yALocation(Ny) As Single

Dim cB, cT, cR, cL As Single

'Definitions

Radius = Range("B2").Value
HalfHeight = Range("B3").Value
Timemax = Range("B10").Value
Alpha = Range("B9").Value
Ti = Range("B4").Value
Te = Range("B5").Value
dt = Range("B13").Value
Pi = 4 * Atn(1)
k = Range("B8").Value
h = Range("B7").Value
Told = Range("C18:L27").Value
Timenow = Range("B15").Value


dr = 2 * Radius / (2 * Nr - 3)
dy = 2 * HalfHeight / (2 * Ny - 3)

'Nodes in Radius'
r(1) = 0: r(Nr) = Radius
For i = 1 To Nr - 1
r(i) = r(i - 1) + dr

Next i
'Nodes in Halfheight'
y(1) = 0: y(Ny) = HalfHeight
For i = 2 To Nr - 1
y(i) = y(i - 1) + dy

Next i
'Locations for sides of volume elements'
rALocation(1) = r(2) / 2: rALocation(Nr) = Radius
For i = 2 To Nr - 1
' rALocation(i) = (r(i + 1) - r(i)) / (Log(r(i + 1) / r(i)))
rALocation(i) = (r(i + 1) - r(i)) / (Log(r(i + 1) / r(i)))

Next i
'Locations for tops and bottoms of volume elements'
yALocation(1) = y(2) / 2: yALocation(Ny) = HalfHeight
For j = 2 To Ny - 1
yALocation(j) = yALocation(j - 1) + dy

Next j
'Vertical areas perp to radial heat flow'
For j = 1 To Ny
For i = 1 To Nr
ra(i, j) = 2 * Pi * rALocation(i) * (yALocation(j) - yALocation(j - 1))

Next i

Next j
'Horizontal areas perp to vertical heat flow'
yA(1) = Pi * rALocation(1) * rALocation(1)
yAsum = yA(1)
For i = 2 To Nr - 1
yA(i) = Pi * rALocation(i) * rALocation(i) - yAsum
yAsum = yAsum + yA(i)

Next i
'volumes'
For j = 1 To Nr - 1
For i = 1 To Nr - 1
dV(i, j) = yA(i) * (yALocation(j) - yALocation(j - 1))

Next i
Next j



'Main Loop of explicit finite difference heat transfer'
Do
Timenow = Timenow + dt
Te = Range("B5").Value
HeatTransferCoefficient = Range("B7").Value
'del
Dim outputregion As Range

'Set outputregion = Range("C14:L23")
Set outputregion = Range("C18:L27")

ReDim arr(i, j) As Single
'del

For j = 1 To Ny - 1
For i = 1 To Nr - 1
Select Case j
Case 1
Select Case i
Case 1

cR = Alpha * dt / dV(i, j) * ra(i, j) / dr
cT = Alpha * dt / dV(i, j) * yA(i) / dy
Tnew(i, j) = Told(i, j) * (1 - cR - cT) + cR * Told(i + 1, j) + cT * Told(i, j + 1)

Case 2 To Nr - 2
cL = Alpha * dt / dV(i, j) * ra(i - 1, j) / dr
cR = Alpha * dt / dV(i, j) * ra(i, j) / dr
cT = Alpha * dt / dV(i, j) * yA(i) / dy

Tnew(i, j) = Told(i, j) * (1 - cL - cR - cT) + cL * Told(i - 1, j) + cR * Told(i + 1, j) + cT * Told(i, j + 1)

Case Nr - 1
cL = Alpha * dt / dV(i, j) * ra(i - 1, j) / dr
cT = Alpha * dt / dV(i, j) * yA(i) / dy
cR = Alpha * dt / dV(i, j) * 1 / (k / (h * ra(i + 1, j)) + (dr / 2) / ra(i, j))

Tnew(i, j) = Told(i, j) * (1 - cL - cR - cT) + cL * Told(i - 1, j) + cT * Told(i, j + 1) + cR * Te

End Select

Case 2 To Ny - 2
Select Case i

Case 1
cR = Alpha * dt / dV(i, j) * ra(i, j) / dr
cT = Alpha * dt / dV(i, j) * yA(i) / dy
cB = Alpha * dt / dV(i, j) * yA(i) / dy

Tnew(i, j) = Told(i, j) * (1 - cR - cT - cB) + cR * Told(i + 1, j) + cT * Told(i, j + 1) + cB * Told(i, j - 1)


Case 2 To Nr - 2
cL = Alpha * dt / dV(i, j) * ra(i - 1, j) / dr
cR = Alpha * dt / dV(i, j) * ra(i, j) / dr
cT = Alpha * dt / dV(i, j) * yA(i) / dy
cB = Alpha * dt / dV(i, j) * yA(i) / dy

Tnew(i, j) = Told(i, j) * (1 - cL - cR - cT - cB) + cL * Told(i - 1, j) + cR * Told(i, j + 1) + cT * Told(i, j + 1) - cT * Told(i, j - 1)


Case Nr - 1
cL = Alpha * dt / dV(i, j) * ra(i - 1, j) / dr
cT = Alpha * dt / dV(i, j) * yA(i) / dy
cB = Alpha * dt / dV(i, j) * yA(i) / dy
cR = Alpha * dt / dV(i, j) * 1 / (k / (h * ra(i + 1, j)) + (dr / 2) / ra(i, j))

Tnew(i, j) = Told(i, j) * (1 - cL - cT - cB - cR) + cL * Told(i - 1, j) + cT * Told(i, j + 1) + cB * Told(i, j - 1) - cR * Te

End Select
Case Ny - 1
Select Case i

Case 1
cR = Alpha * dt / dV(i, j) * ra(i, j) / dr
cB = Alpha * dt / dV(i, j) * yA(i) / dy
'cT = Alpha * dt / dV(i, j) * 1 / (k / (h * yA(i + 1, j + 1)) + (dr / 2) / yA(i, j))
cT = Alpha * dt / dV(i, j) * 1 / (k / (h * yA(i)) + (dr / 2) / (yA(i)))

Tnew(i, j) = Told(i, j) * (1 - cR - cB - cT) + cR * Told(i + 1, j) + cB * Told(i, j - 1) + cT * Te

Case 2 To Nr - 2
cL = Alpha * dt / dV(i, j) * ra(i - 1, j) / dr
cR = Alpha * dt / dV(i, j) * ra(i, j) / dr
cB = Alpha * dt / dV(i, j) * yA(i) / dy
cT = Alpha * dt / dV(i, j) * 1 / (k / (h * yA(i)) + (dr / 2) / yA(i))

Tnew(i, j) = Told(i, j) * (1 - cL - cR - cB - cT) + cL * Told(i - 1, j) + cR * Told(i + 1, j) + cB * Told(i, j - 1) - cT * Te


Case Nr - 1

cL = Alpha * dt / dV(i, j) * ra(i - 1, j) / dr
cB = Alpha * dt / dV(i, j) * yA(i) / dy
cR = Alpha * dt / dV(i, j) * 1 / (k / (h * ra(i, j)) + ((dr / 2) / ra(i, j)))
cT = Alpha * dt / dV(i, j) * 1 / (k / (h * yA(i)) + ((dr / 2) / yA(i)))

Tnew(i, j) = Told(i, j) * (1 - cL - cR - cB - cT) + cL * Told(i - 1, j) + cR * Told(i + 1, j) + cB * Told(i, j - 1) - cT * Te
End Select
End Select

Next i
Next j
For j = 1 To Ny - 1
For i = 1 To Nr - 1

Told(i, j) = Tnew(i, j)
Next i
Next j



arr(i, j) = Tnew(i, j)


outputregion.Cells(Nr, Ny).Value = arr(Nr, Ny)


Loop Until Timenow >= Timemax


End Sub










[/PHP]