FORTRAN in UNIX

Hi,
Please excuse me if you think this net is an appropriate place to post the
following question.

I am working on a fortran program under SPARCompiler environment. I want to
use a system call in which the parameter is a variable. For example:

      call ('uncompress filename')

where filename is variable whose value is assigned in a previous statement.
This doesn't work. However, it is ok when I replace variable filename with an
actual file name. Could anyone tell how to use system call in which the
parameter is a variable.

Thank you very much.

Ye Qi