(stabbing in the dark) Would this make any difference?

IF !EMPTY( this.control_source )
	cAlias = SUBSTR( ALLTRIM(this.control_source), 1, AT('.',ALLTRIM(this.control_source)) - 1)
	* 1. Check to see if cAlias is blank
	IF EMPTY(cAlias)
		= MESSAGEBOX("cAlias is empty", 0, "test")
	ELSE
		* 2. A different approach to checking if workarea is open
		IF NOT USED( cAlias )
			= MESSAGEBOX("Alias "+cAlias+" not open!", 0, "test")
		ELSE
			cControlSource = ALLTRIM( this.control_source )
			IF EVALUATE( cControlSource ) == OLDVAL( cControlSource )		
				RETURN .T.
			ENDIF 
		ENDIF
	ENDIF
ENDIF

>>>>Hi,
>>>>
>>>>Could someone suggest why I am having a problem (actually not me but the customer) in the following segment of code:
>>>>
>>>>The container with the text box has a property control_source. This property has a value V_WORK.EMPLOYEE
>>>>
>>>>The code then checks is the value of the field EMPLOYEE in the cursor V_WORK has been change. Here is the code:
>>>>
>>>>

>>>>		cControlSource = ALLTRIM( this.control_source )
>>>>		IF EVALUATE( cControlSource ) == OLDVAL( cControlSource )		
>>>>			RETURN .T.
>>>>		ENDIF 
>>>>

>>>>
>>>>The problem occurs on the line above, EVALUATE( cControlSource ) == OLDVAL( cControlSource ), and it does
>>>>ALIAS IS NOT FOUND. I verified that the entry in .control_source exists as described above.
>>>>
>>>>TIA.
>>>>
>>>>UPDATE. the following code checks that the alias V_WORK exist and is open. This code, below, is before the code above (just in case someone wonders if the alias is indeed exists and open
>>>>

>>>>
>>>>IF !EMPTY( this.control_source )
>>>>	cAlias = SUBSTR( ALLTRIM(this.control_source), 1, AT('.',ALLTRIM(this.control_source)) - 1)
>>>>	IF SELECT( cAlias ) > 0
>>>>		cControlSource = ALLTRIM( this.control_source )
>>>>		IF EVALUATE( cControlSource ) == OLDVAL( cControlSource )		
>>>>			RETURN .T.
>>>>		ENDIF 
>>>>      ENDIF
>>>>ENDIF
>>>>

>>>
>>>I added - for testing - a TRY / CATCH around the above code. Then modified the line:
>>>

>>>cControlSource = ALLTRIM( this.control_source )
>>>

>>>to a bogus:
>>>

>>>cControlSource = "test.test_field" 
>>>

>>>
>>>And the error caught by the TRY / CATCH, says "Alias 'test' not found".
>>>But the error that the customer saw (without a TRY /CATCH) did not have the "bad" alias name. It was simply:
>>>ALIAS IS NOT FOUND
>>>
>>>Any suggestions?
>>
>>Could there be a possibility that the control_source property be assigned a value other than what you're expecting it to be (in particular when the code is run at the customer location where the orignial problem is occurring) ?
>>could there be a possible problem like "pointer aliasing" going on?
>>

>>* object "foo" contains object "bar" which in turn contains object "baz".   Object "baz" has property named "propname"
>>foo.bar.baz.propname = "some value"
>>= SubProc( foo.bar.baz )
>>* value of "propname" property would have changed.
>>
>>FUNCTION SubProc( yuck )
>>    yuck.propname = "other value"
>>ENDFUNC
>>

>
>I don't think the above scenario is possible. But I will think of it.
>Thank you.