How to make more color

Hello, all expert, I am using the Excel 2003 worksheet to make a project.
But due to the limintation for the conditional formatting for the color
therefore need your help...

Is there anybody can help me ?
Problem as below..
How to change each cell color by just key in the
specific rank " alphabet " ?
Example:
Rank A = Grren Color when Key in " A "
Rank B = Blue Color when Key in " B "
Rank C = Yellow Color when key in " C "
Rank D = Red Color when key in " D "
Rank E = Orange Color when key in " E "
Rank F = Pink Color when key in " F ".

Thanks in advance
P/S: I am totally new in VB.