NaN and Infinity in my Report

I am using Visual Studio to build my report and I have tried this:-

=IIF(Fields!A.Value =0or Fields!B.Value =0,0,SUM(Fields!A.Value)/SUM(Fields!A.Value)&=IIF(SUM(Fields!A.Value)=0or SUM(Fields!B.Value =0),0,SUM(Fields!A.Value)/SUM(Fields!A.Value)&=Replace(Round((((SUM(Fields!A.Value)/SUM(Fields!B.Value)))*100),0),"NaN","0")+"%"

The first 2 give me only 0% and the last one doesn't get rid of Infinity but does get rid of NaN.

Can someone please help where I can use both these expressions together and get rid of showing 0% and also NaN and Infinity.

Thanks