Rules - Test for Replay

[K.W.]

Is there a test that can be used to determine if the current Session is currently under Replay? 

I want to rePOST some POSTs but I want to change a value each time, so, I'd like to do something along the lines of:

static function OnBeforeRequest(oSession: Session) {

If (oSession.Replay) {

     oSession.utilReplaceInRequest("cookieMonster:1234567","cookieMonster:987654");

}

....

}