Best way to populate worksheet from 2 combo boxes

I am creating a rate sheet that currently uses just one combo box and "if"
formulas.
Rates are A, B, C, D, E and the formula is
=IF($J$3=1,Data!$C$2,(IF($J$3=2,Data!$D$2,IF($J$3=3,Data!$E$2,IF($J$3=4,Data!
$F$2,IF($J$3=5,Data!$G$2,IF($J$3=6,Data!$H$2,"")))))))

J3 is the output from the Combo box.
I have 81 products that are listed on the Main worksheet, each with this
formula so that when a Rate is choosen from the Combo box then it populates
the Main worksheet with the appropriate data.

All of this works beautifully. Until....

I currently have the rates calculated on a weekly bases, but there are some
clients that need to be bi-weekly, or bi-monthly or even monthly.

So.....
I wanted to create a 2nd Combo box and have those 4 options. Use that data
from that combo box in conjuntion with the data from the first combo box to
populate the worksheet.

I created an IF formula, but by the time I got it all in like I needed it,
Excel said it was too long.

I know that I could create 4 different worksheets one for each of the "time"
varable, but I would like for it all to be on one sheet. (I am catering to
the least common demoniator in the office )

I have looked the the postings and couldn't really find anything that matches
this problem.

Here is what I got right now:
http://www.oakhillphoto.com/6ClassRateSheet.xls

If there is a better way to do this I am willing to learn.

Thanks in advance.