Insert two lines of total

Hi, I have a simple query like this:

               Char A     Char B     Result

Char 1      X               Y          X+Y

Char 2     Z               W          Z+W

Result    X+Z          Y+W

And I want to insert other line of result with % of each char, like this:

                    Char A                    Char B          Result

Char 1           X                              Y               X+Y

Char 2          Z                              W               Z+W

Result         X+Z                         Y+W               Grand total

Result %      X+Z/Grandtotal      Y+W/Grandtotal     100

How can I do that?

Thanks

Dora