javascript regx in getelementbyid ??

i have a span which contains as in hidden field

<span name="pc_fields" id="profit_center<%=pc.id%>_span">
<%= hidden_field_tag "profit_centers[#{pc.id}]", pc.send(percent_field) %>
<%= hidden_field_tag "profit_centers_#{pc.id}_locked", 1 %>
</span>

and this span is in a table row so there will be more than one span

now i have in javascript i have like
var all_pcs = document.getElementsByName('pc_fields') this wont work in IE .

so i want to write some thing like this
var all_pcs = document.getElementByid('profit_center'*'_span').

thanks in advance for you help.