How to control double data entry using checkbox

Dear all

I have a application where I am collecting fees for 12 month using chkBox, janCB for January and so on after checking box fees is added to FeesTextBox.Text and inserted to DB under sr/id=1 when I reopen the application I want that for ID=1 my janCB should be lock but for entering new it is again enable

inshort

whatever chkbox I have used to enter data on 1st transaction should be un editable for that particular id under binding navigator to control duplicate entry under same ID

how to do that.

thanks

sunil