#Error for Division Cell in Report

Hi All

I am trying to use this expression in Report Builder 3.0 (SSRS 2008 R2), however get a #Error message because its a division;

=SUM(Fields!Project_Work.Value) / (SUM(Fields!Project_Work.Value) + SUM(Fields!Admin.Value))

How can I avoid the #Error message? Looked on the internet but haven't quite found the right format to sort it?