If I understand the problem you are looking to get something a bit like this, where the totals for Group1 are all different - but all shown as 100% bars:
Many thanks to NMiller who posted the solution here: http://community.qlik.com/forums/p/24590/93940.aspx#93940
Use the expression: SUM(Value) / SUM(TOTAL <Group1> Value)
The Total part is telling the expression to ignore the dimension, but the <Group1> is tying the second SUM to that dimension.
Hope that helps.