I have this formula in a cell of validation and I need it to let in a time in this format 12:00-18:00 which this current formula does but I need it to let in the word hol to

=IF(F4="",,(IF(OR(F4="Holi",AND(TIMEVALUE(TEXT((TIMEVALUE(RIGHT(F4,FIND("-",F4)-1))),"hh:mm"))=TIMEVALUE(RIGHT(F4,FIND("-",F4)-1)),TIMEVALUE(TEXT((TIMEVALUE(LEFT(F4,FIND("-",F4)-1))),"hh:mm"))=TIMEVALUE(LEFT(F4,FIND("-",F4)-1)))),TRUE,FALSE)))

thanks