Hide Field and TextField in PA20, PA30 through screen control.

Dear Experts,

I want to hide Pers.Assgn and textbox and other two icons.

I checked in "Change screen control" and "change screen modification".

I got the label and textfied tech information from below mentioned screenshots

I know to hide the field .but how to find the parameters to control infotype PA20, PA30, PA40

how can i find the exact place to make changes on the preferred screen?.

Please provide screenshots if it is possible.