CV01N screen object link field mandatory

[so8vishalthakur]

Hi Experts,

Here I am stuck with one requirement in the given image I have to make the object Links tab Input field mandatory.

I have tried the Transaction & screen variant and also i tried making input as required in Screen Painter, this works only if the user goes inside this tab, if the user gives input only in the Document data tab and tries to save it will let him save the document. Please suggest any solution to make get a popup in the main screen if the data if not input field are initial in Object link Tab.