CrossTab reports Using TM1 as source

[evergreen]

Level 3 - Department
IT   

Level 4---Department –IT
IT- developers,
IT- programmers,
IT-Analyst   

Level3 --Location State-
Texas

Level4  Location- City
Houston,
Austin,
Dallas   

In the Prompt, We have IT -Department prompt and Texas - Location Prompt
                 



I am a new bee to cognos report studio.  I want to achieve the above items to be displayed in crosstab, I have two value prompts that shows only the level3- Department and Level3- Location and we have multi select option in the prompts. We don't need to show the level 1 and level 2 in the prompt. Thats the reason, It should show Only level 3 and level 4. Thats the reason, I've used value prompt instead of tree prompt.
I've used Levels function in the prompts filter. When I drag the Level 3- department and Level 4 Department to the crosstab, then the report is working fine. But when I drag the level 3-Location or Level 4- Location to the crosstab then it takes forever to run  and keeps running for more than 2 hours.  How can it be achieved? Please help.