You can simply add "zCF_DimSelected" to the filter. (Parameter controlled dimension)
However, the issue is how to rest filter I believe, which you can get info fro this link.
Thanks Shin and Pavan, Your suggestion works but I did not give you the whole problem.
I gave a brief explanation of the problem as its a complex report.
The State is not part of the filter, it is always displayed for all the three filters.so I removed it from the Parameter list.
I forgot to mention that when the user selects say Events(sP_SelectDim) two dimensions need to be selected.
1) The Event Dimension
2) The Flag Dimension has to be SET to say "E" (this dimension is not in the base file).
Guys I solved it by creating a boolean condition CF.
Thanks for your assistance. I will close this as solved.