Help on using VPWL_F_RE_FOREVER

Hi fellow designers! I get this error message while using the VPWL_F_RE_FOREVER. ERROR -- Invalid Time (.STIMULUS) in file "ordino_stims.stl" Line 13 I've spent hours browsing the PSpice Manual but there is no detail about VPWL_F_RE_FOREVER that could help me figure out the problem. Your advice will be highly appreciated. Thank you!