Change Line Style in my graph

I am trying to change the line style in my graph. My users do not want colors. So, I used grayscale and I am trying to change the line style to differentiate. Is not working and I am not sure whats going wrong..

This is what I used.

=IIF(Fields!CollectionPointNumber.Value = 0, "Solid", (IIF(Fields!CollectionPointNumber.Value = 2, "Dotted","DashDotDot")))

This website says it should work but its not working for me.

http://stackoverflow.com/questions/15941291/using-different-line-styles-instead-of-colours

Any help?