THIS STATEMENTS RETURNS A FALSE =IF(C412="mem",IF(AND(EJ412>Sheet1!$E$19,EJ412<Sheet1!$F$19),"PM",IF(AND(EJ412>Sheet1!$E$20,EJ412<Sheet1!$F$20),"PM",0)))

OK, had my morning coffee, try this:
=IF(C412="mem",IF(AND(EJ412>Sheet1!$E$19,EJ412<Sheet1!$F$19),"PM",IF(AND(EJ412>Sheet1!$E$20,EJ412<Sheet1!$F$20),"PM",0)),"")
