>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 could never duplicate the problem (above) on my system. Borislav came the closest to explaining why the problem occurred; even though his code error message was different than what the customer would get.

I changed my code, as suggested by many, replaced the OLDVAL ("V_WORK.EMPLOYEE") with the OLDVAL() and two parameters, parsing the "V_WORK.EMPLOYEE" into two values. I enclosed the new code into TRY CATCH (just so that the customer does not see the error, but I can read it in a hidden log).
So far, after two days, the new code works and no error in the hidden log.
I may remove TRY CATCH at some point as I understand that it slows down the processing. Although nobody yet complained.
Thank you all for your help!