Calling Java from other programs

Hello. I am sure this has been asked numerous times before, but I am
unable to find a conclusive answer. Please forgive me if this info is
available elsewhere.

I am developing a model to be used by others within my company.
Because the end users are sort of a mixed bag with respect to
technical backgrounds, we generally present everything in MS Excel.
While Excel comes with VBA, I find this language cumbersome and
annoying to develop anything larger than a few lines. My program of
choice is Java. My question is, how can I do my development in Java,
then compile the results into an executable that I could subsequently
call from VBA? My boss (who is somewhat old school with repect to
programming) does a similar thing using Fortran 90. He is able to
generate a DLL file which allows him to pass all of the needed
parameters to his Fortran routine from VBA. Can I do something
similar with Java?

Thanks in advance for any help.