How to disable/read-only check box in Receiavbles receipt application forms

HI,

1- I am trying to freeze the check box of apply in receipt application form but it  is not working properly some times its working fine and some time it is not. I am using when new record instance when I am using up arrow and down arrow key it is working fine, but if I am on first record and click the mouse on second row or third row using mouse It is not working and user can un- apply the receipt

2- Due to 1 point I tried using disable that check box but it is show some error 'frm-41017 cannot set update allowed attribute of non-enabled item'.