Have you tried setting the ParameterLanguage in the URL?

This forces it to accept the paramter in the desired format.

e.g. rs:ParameterLanguage=en-GB

Somehow you have a special character in between the "and" clause and where you line break. Just delete it so the expression is on one line i.e

=iif(Fields!Target.Value*100 = 0.0...

You don't need to use a pivot command, the chart tabulates the data for you with the Category and Series Groups and value summary. You can also filter on...

http://www.codeproject.com/Articles/10135/Not-Another-C-Versus-VB-Article?msg=3050761#xx3050761xx

The article is the usual C#/VB snobbery and in-fighting but the linked reply makes some good points in the case for VB.NET.

Comparing the two is always invitation for...