Has anyone a solution to reference issues such as this:

I was asked to create a tool using Solver for use by a co-worker & his
department. They are all using Office 2003 while I am on Office 2007.

My code must reference the 2007 solver add-in, Solver.xlam, while to run on
their PCs it must reference solver.xla. Each round of testing requires that
the tester go thru the steps of 'de-referencing' the xlam and referencing the
xla.

Is there a technique for "conditional referencing" depending on the version
of Excel?