Hello Visual Basic expert ;)

I am searching for a way to input data in the Grid of my program (see
attachment). I want to input some x and y values in those cells, and
calculate an equasion (Vergelijking) from them.

When I run the program, I can select the cell, but I can't seem to
type anything in it : HELP !

Also, I would like some advise about how to link the nulbers typed
there to the equasion wich should appear in the textbox.

Thanks in advance,

Rule