Please read the Forum Guidelines. You gave no information as to which tool you are using - if it's a Cadence too, it could be Diva, Assura, PVS or Dracula. Or it maybe you're using Calibre (Mentor) or Hercules (Synopsys). The name "PEX" tends to be used by Calibre, so that would be my wild guess. Also the version of the tool is important (as explained in the guidelines).
Otherwise it's very hard for anyone to give you help. This may not even be the best forum (particularly if it's a non-Cadence tool).