Thanks Hilmar!

But your answer looks like doesn't solve my problem. My problem wasn't happened in new recode. Ok , let's get more detail, I was used method like the next in a textbox's valid method:

LOCAL nChanged
nChanged = GETFLDSTATE(this.ControlSource)

IF nChanged > 1
thisform.ocurnode.text = ALLTRIM(this.Value)
ENDIF

Like you see, ocurnode is a refrence to a treeview control's selected node.When i changed the text of the textbox, i want the node's text also to be changed.The problem was happened then.:-(

Thanks again!