checking dependencies

[garima cse iitb ac in]

hi

i want my rpm to check certain softwares installed and then only it should
install.
i used Requires prefix in my spec file but it can check only for the
packages installed by RPM,not through a tar.gz file.
can someone plz give a script or so that can check for these dependencies.
for ex. i want j2sdk1.4.0 or greater should be installed before my rpm
etc.

regards
garima