How would I change the color of a block of cells with one click of the mouse
and then the next click a different color?

Example cells
on my excel 2003 page 7,8,9/DEF make a block. I need the first click in the
block to change the background green and record the Date/time somewhere else,
2nd click in the block the background will turn blue, time/date are recorded
( I will need them for later calculations) the 3rd could change it back to
white, make a cycle or RED and not change from red, to signal the other
time/date stamps are going to be inaccurate