Printing SapScript from a Function

Is there some limitation that prevents SapScript from accessing host variables when called from a function?

Background

I wrote program to print a simple SapScript form with data that works well. I translated that source code into a function called ZDUN_PRINT_PD_LETTER. When I execute this function the form prints but none of the host variables come through to the form. Everything looks in order to me.

Thank you.

Crew Reynolds

Daydots