You probably have Option Explicit at the top of your userform  module,
which demands variable declaration.

You should ALWAYS have Option Explicit in all modules, it is a bad idea
to rely on implicit variable declaration.

It's difficult to see what you are doing, and especially why it would work
in 2007, but not in 97. There might be a different incompatibility.

Essentially, you should not expect a spreadsheet (particularly a macro  in a
spreadsheet) to be able to work with two versions of Excel so far apart.

You should not be looking at ways to use variables  without declaring  them
somewhere. They really should be declared, and then the compiler can assist
you in finding programming errors.

However, you should only declare variables in one place. If they need
global scope, make them public.