It must be early monday morning because I can not wrap my head around this.

I have a spreadsheet that has due dates and pay dates that are different
depending on sales rep. This is an example:

A B C D E
1 customer sales rep inv date due date pay date
2 misc 1 SLS 11/30/2009
3 misc 2 HOU 11/30/2009
4 misc 3 NAG 11/30/2009
5 misc 4 KAS 11/30/2009



Sales Rep SLS always gets paid on the first of the month following the
invoice date.
Sales Rep NAG always gets paid on the 15th if in by the 30th and paid by the
30th if in by the 15th.
Sales Rep KAS and HOU is net due 30 days.

Can anyone help?