Simple Query Result set as a %age of another result set

Dear All,

Query A is returning 3 key figures only (nothing in the rows) but with a filter on Customer in the free characteristics.

Query B is returning the same key figures still with customer in the free characteristics but without a filter.

I need query C to put the corresponding key figures from A over B and return a percentage.

This needs to be done in the query and cannot be done in update rules.

Can anyone help...?

I of course will award as many points as I can to the first solution!

Many thanks in advance,

Stuart Humphrey