Textbox Data Not Refreshing

I have two textboxes...on the textchanged event of one textbox, readonly property of other textbox gets defined...e.g. first textbox is retrieving data as add,update,delete...when the first textbox text is changed to update then & then only second textbox readonly property is set to false...Now the problem,I am facing is....whenevr first textbox text is add,delete,its working fine..& second textbox is fetching the correct data..but once first textbox data gets changed to update,second textbox data remain unchanged though its readonly property gets changed correctly..it shows the same data as it was showing the first time when first textbox was changed to update...but after that,its data is not changing.