Using Variables in Advanced Queries

[#1]

I have set up ACT with sixteen order history lines.  I want to check that the expiration date is on or before a particular date in the next month.  Your customer service representative indicated we cannot use a varialbe date As it is, the line reads "If Exiration Date is on or before 9/15/2011 - I would like to have a list of Virable Fields that I can use in a lookup, including a date lookup...  Another solution would be a variable placed as a field in the contact record.  Now, if you create a "Last Lookup Date" and do a global change to the date you want, you cannot use the field in the date lookup.

As it is, I will need to change every line (16) of the inquiry changing the date.