Hi,
I recommend using crosstab reports in case the number of columns is varying about the data in a table.
For example, i had to make a report from the payroll. The data's organized so that every record has EMPLOYEE, TYPE-OF-TRANSACTION, AMOUNT (just for example). I used i cross-tab so for every TYPE-OF-TRANSACTION the report will grow a column.
I hope i've been clear enough.
Good luck.