GOT IT

Thanks Sky. I was forgetting to divide by the width and height to get the start location of the grid.
Now I have a re-sizable grid that tells you the square you click on and all the squares around it.
I think I should be ok from here.
I have had a couple of ideas how to proceed.
I am going to use 2 grids. One visible and then one over the top invisible. The visible one won't do anything but look pretty. The invisible will detect the clicks and then I can use this to add things into the grid. Not sure if this is the best method but I was finding if I added an actor to a grid square it would register the mouse clicks on the actor rather than the square.
I want to get the hang of this linked list/ structure method so I was thinking of using a loop at the start which builds the structure telling each square its top,bot,left and right values. Then change the mouse clicks to find the adjacent cells from the structure.(if that makes sense)
I need the cells to register another value based on the actor attached to it which is why I am going to try this method. If I can't work it out I will use an array to register the value.
There may be some areas that I struggle with at a later stage. 1 is the AI. it's a 2 player game. I may just make it 2 players with no computer player.
The 2nd is the timing of an event. This will make sense when I get further through.
Right now though I am ready to progress so thank you all who helped especially Sky and Evan . I'll upload a demo as soon as there is enough going on to show what I am aiming for.