How about including the state codes within the option values for each institution option?

Say you encode your "institution" field along these lines:

I001AZ, Institution 1, Phoenix, AZ
I002MS, Institution 2, Minneapolis, MS
I003MI, Institution 3, Detroit, MI
...

You can then just grab the state from the right two characters of the field value:

@CALCTEXT(right[institution,2))

Just be aware that non-integer values can't be labelled if you want to export to Stata. Otherwise they don't tend to cause any drama.