Hi,

Yes, this can be done. There are a number of ways you could do it, and it depends on whether you are using Formulas or the built-in summary types. From your post, it looks like you are using the built-in types, so the easiest thing to do in that case would be to use an External Summary.

I have attached a quick sample that demonstrates how to do it. Note that my sample assumes the grouping structure. It's using the sum of the group and dividing by the grand total which is the sum of ALL of the rows in the grid. If you have multiple levels of grouping, this might not be what you want, and if you have no grouping, I'm not entirely sure what will happen, but it won't be correct. :)