cascade parameter are not refreshing correctly

Hi,

I have created cascade parameters (p1,p2 &p3) in SSRS and added mdx query to set defualt value in p2 & p3
When I used a dynamic mdx query to set default value, then p3 is not refreshed dynamically and it shows previous values itself.

But when I removed default values its working correctly.

Is this issue related to dynamic query?.Any suggestions?.
Any help is appreciated..

Thanks,
pvn