You can put a sleep in there to clear the message.
Dim Inch_LED_boolean As Boolean
Inch_LED_boolean = GetOEMLED(801)
If(Inch_LED_boolean = True)Then
MESSAGE " Went Into Inch Mode"
...you might want to use a userlabel or ticker as well as well.
In Screen4 you'll want to drop a Userlabel or ticker:
SetUserLabel 12, "You must enter a whole number of holes"
SetTicker 205, "This is a very long error message because you seem to have done something very silly"