I am using a drop down list with text descriptions. I want to set up a
system to say that "if" a certain selection is chosen then a date will follow
each being different:

For example:
drop down contains two selections 1. Payment Due 2. Payment due net 30 days.

I want to make the appropriate date calculate based on the option I choose
from the drop down. all ship dates are realtive not only to the drop down
choice, but the date the order was entered