I can navigate cells using the arrow keys but I still have to click on the cell to edit it.
Is there a way to have the cell open for edit when you type something or enter numbers?
You can press the space bar to begin editing. Anything beyond that would be pretty complicated, because the edit control is not created until editing starts. This means you would need to cache the key press, start editing, then feed the keypress to the edit control and hope it knows what to do with it. Not impossible, but fraught with peril.