Action security with unexpected behaviour

Hi List,
I have another security question.
I have applied action security for all actions (Delete, Copy, Add, Change) on Form W41016WA, which is a "Headerless Detail Form" type. This form also has a grid where information can be typed in. I need this form to be "read only" for most users.
Problem is that when I enter this screen and there is no information, the user can type in the grid and save the data. Only when there already is some data in the grid, security works as expected. Why does security behave different for screens with data vs screens without data ?

Thanks for any input, Gerd

E8.9, SP3, AS400, WTS

Hi Gerd
In some forms the "OK" button controls whether you can modify the contents or not. I suspect this is one of those forms.
Ok button is controlled by 2 type of action security(Change and select). If the data is already there then "Change" security controls this button. But if you are entering the new data then "Select/OK" security control this button. Make "Select/OK" action security = N for this form and it should work.