Application Express :: How To Use The Result Of A Sum In A Classic Report

I've created a classic report that sums a couple of columns in two different regions:(Why can't I insert an image?)This is a simple example:

Region1col1     col2     col3     col4     col5    a          b          20          5          25%c          d          40          4          10%e          f          120         6            5%report total:     180          15          x Region 2col1     col2     col3     col4     col5    g          h          30          6        20%i          j            70         14       20%report total:     100        20          yMy

How do I access the values generated by APEX (in bold) so that I can use them in further calculations? e.g. create a grand total from both regions

2) Having calculated a value, assuming 1 above is possible, how do I insert it at position x or y? e.g I want to calculate a % so that x would be 8.33% and y 20%

3) How do I change the words report total