sheet.cells(index1,index2) overflow error

I have a macro that generates a lot of output
for each case(c) there are multiple iterations(i) that need to be transferred to an output worksheet

the reference for the output area is of the form

with worksheets("sheetx")
.range(.cells(caseNumber * iterations+spaceRow,columnIndex),.cells(caseNumber*iterations+iterations+spaceRow,columnIndex2))

iterations is a user-defined constant, and case_number is the the number of cases run thus far.
neither iterations nor case_number exceed the limit for an integer, but when their product exceeds 32701, I get an overflow error

I'll try setting caseNumber and iterations to long, but if that works, what's up with that?