Error With Subtotal And Grand Totals With Iff Checking.

I have a table with amount columns and I want the amount column to either insert the value from the database or a zero based on a condition.



For the table rows I use the following to find the amount:



=iif( Fields!TYPE.value="Material" or Fields!TYPE.value="Other", FIELDS.Amount.Value,0)



which works fine. However, when I try to Sum in the group foot I get #Error when I use



=sum(iif( Fields!TYPE.value="Material" or Fields!TYPE.value="Other", FIELDS.Amount.Value,0) )



for the groupings that have a type other than Material and Other. For some reason, it doesn't total the amounts of Material and Other with the Zeroes that were placed in the table rows based on the Condition.



For example, the subtotal errors out when trying to total Material with Labor but if it was just Material and Other, it works.



Example of what the Columns are:



job, year, month, type, amount



s57, 2007, 2, labor, 0

s57, 2007, 2, material, 500



month total errors out

year total errors out

job total errors out



Any help would be appreciated.