Well you have Dim grid.tile(5,5) I hope.
Then you convert the mouse position to a tile index.
Local mousetile.tile
mousetile=grid(mousex()/tilewidth,mousey()/tileheight)
Now mousetile points to the tile the mouse is over.
Print mousetile\letter
Then you convert the mouse position to a tile index.
Local mousetile.tile
mousetile=grid(mousex()/tilewidth,mousey()/tileheight)
Now mousetile points to the tile the mouse is over.
Print mousetile\letter