You have to prevent totsum from being 0, since that is what is causing your divide by zero #ERROR's.
If you want that to evaluate to 0 then try:
=iif(sum(Fields!Deqsum.Value) = 0,0,
(SUM(Fields!Deqsum.Value) *iif(SUM(Fields!Totsum.Value)=0,0,1)
/
iif(SUM(Fields!Totsum.Value)=0,1,SUM(Fields!Totsum.Value))))
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Your lack of planning does not constitute an emergency on my part...unless you're my manager...or a director and above...or a really loud-spoken end-user..All right - what was my emergency again?