Did you try (note the alltrim and str functions added);

     Select Hesab01
     SET FILTER TO GCode = ALLTRIM(STR(thisform.y_GCode)) .AND. !EMPTY(KCode) .AND. EMPTY(MCode)
     thisform.list2.ControlSource = "Hesab01"
     thisform.list2.RowSource = "KName"

>Hi all
>I have a problem with filter command. when i use from below command in my form
>
>

>     Select Hesab01
>     SET FILTER TO GCode = thisform.y_GCode .AND. !EMPTY(KCode) .AND. EMPTY(MCode)
>     thisform.list2.ControlSource = "Hesab01"
>     thisform.list2.RowSource = "KName"
>

>
>i get not correct filtered records, but if i change it as below
>
>

>     Select Hesab01
>     filterStr = "SET FILTER TO GCode = " + ALLTRIM(STR(thisform.y_GCode)) + ;
>     " .AND. !EMPTY(KCode) .AND. EMPTY(MCode)"
>     &FilterStr
>
>     thisform.list2.ControlSource = "Hesab01"
>     thisform.list2.RowSource = "KName"
>

>
>my list2 filled with right records. i know it is because of GCode = thisform.y_GCode , but why it is wrong?
>thanks for your help