You can use Expression Manager to both calculate the result and pipe it into the question text. If you are using the default sub-question codes in Q04, try inserting something like this in the text of Q05:
Code:
{Q04_SQ001/sum(Q04_SQ001, Q04_SQ002)}
Cheers,
Tony Partner Solutions, code and workarounds presented in these forums are given without any warranty, implied or otherwise.