Process Message Macro

Dear Macro Gurus

I need a message prompt when a user enters a value in a cell.

Condition is

In the header IF NOT

At least one value of Char 1 selected AND

At least one value of Char 2 selected OR

At least one value of Char 3 selected OR

At least one value of Char 4 selected.

Prompt a message: "You cannot make a change at this selection"

or more generally is there a way to gray out key figure input based on the characteristic drill down situation for a logged user?

Real example.

A salesperson is expected to enter an "adjustment" by selecting at least one product and one channel or one customer... these are the characteristics in a particular data view.

Thanks

BS