Tile editor isometric test

Well since I'm waiting for models on my 3D game or moreso waiting to figure out how to get the models, I figured I try to do an isometric version of my editor and tile engine.

Here is my first test and so far it looks ok. The row and column numbers are correct in this screenshot.

However I really have no idea how to convert from mouse x,y to row,col. Once I figure that out I should be able to simply call a Calculate function which will transform coords from mouse x,y to row,col based on the current view mode.

Just toying around and not sure how far I'll go with it.