combining two form inputs

[Blake]

I need to combine two form inputs into one.

For instance, my input form has two drop down menus. The first menu produces
a four-character string and the second menu produces a two character string.

All I want to do is combine the two strings menu1+menu2 into a six character
"hidden" input.

Can anybody help me? Anybody have a script that would do it?

Thanks in advance!
Blake