Installshield Silent uninstall help

[jdobros]

I have a program called tapeprep and i am trying to uninstall it silently. this is the uninstall string in the reg:

C:\WINDOWS\uninst.exe -f"C:\Program Files\Tapeprep\DeIsL1.isu" -c"C:\Program Files\Tapeprep\_ISREG32.DLL"

I have tried /q /s -s -S and have put them all over the above string... can anyone show me the proper format to uninstall this silently?