HI alexander,

Try putting your code directly into the valid event of the textbox. Then use RETURN .F. OR Set a flag in the procedure:

ELSE
WAIT WINDOW "No Matching Customer Found."
Thisform.txtCustno.Value = ""
did_not_get_it = .T.
ENDIF

In the valid event after the call to the procedure do

THISFORM.m_query
IF did_not_get_it
did_not_get_it = .F.
RETURN .F.
ENDIF

HTH
Mike