Lets make this very simple. I have two cells. Lets call them A1 and B1. I
want the cells to be blank or contain just "X". Anything else should not be
allowed. This i can solve by making a validation rule.I have solved this just
by makeing a list that just contain "x", so you get a dropdown box with just
x in it.

But both cells cant contain "X". This can i allsow solve by makeing a
validation rule.
Here i just added =A1="" in the validation. And offcourse i can add =B1=""
in the other valiation cell.

The problem is that i cant solve both. Need help with this one. Plz.

I dont want to use buttons..cuz this will apply to over 1000 cells.