Is it possible to use mathematical operators within picklists?

Hi all

I'm trying to capture in market dates through a form - for example:

0-3 months

3-6 months

6-9 months

Etc.

What I would love to do is take these values from a picklist and using some quick maths, put them into a field in the database. For example:

0-3 months = the date value of TODAY + 3 months

3-6 months = the date value of TODAY + 6 months.

Etc.

Is this possible? I know there is a mathematical operator app, but I haven't seen any reference to picklists and I'm not sure if this functionality is possible.

Thanks

Phil