SELECT customers
LOCATE
LOCATE FOR ALLTRIM(last_name) == ALLTRIM(thisform.txtSearch.Value)
lcCustID = IIF(FOUND(), customerid, [])

SELECT orders
IF !EMPTY(lcCustID)
LOCATE
LOCATE FOR customerid == lcCustID
ENDIF

or

SELECT * FROM orders WHERE customerid IN ;
(SELECT TOP 1 customerid FROM customers WHERE ALLTRIM(last_name)==ALLTRIM(thisform.txtSearch.Value))


Regards,
Onytoo