Did you create the 2 parameters before referencing them in the calculated field? I am guess that`s what you might be missing.
Create the Select Dimension 1 and Select Dimension 2 parameters and that might help.
Let me know if this doesnt work!
I figured out the Dimension issue. It was a bone head mistake. However the chart still isn't drawing at all, it's just blank and I'm not sure why.
I may have to just play with it more