Aggregation and Count Distinct Function

[#1]

I would like a textbox in the presentation layer to count distinct employees present in both time period. The text that says 4 I need to get the answer as 2, as you can see from the table only 2 employees overlap in the time period.

The time periods are given as input box providing the users the flexibility to change time periods.

Any help will be greatly appreciated!

[Gysbert_Wassenaar]

See attached qvw

[#3]

Thank you very much. This greatly helps. As a followup

The actual question I had was to add a third dimension called grade and incorporate the same in the expression.I have attached the file for your reference.

I need two text boxes -

First Expression - I want to count the employees present in both time periods with same grade in both periods - The result should be 1 as you can see EmpID 2 is the only one that fits this criteria.

Second Expression - I want to count the employees present in both time periods and with only positive increase in grade points - The result should be 1 as you can see EmpID1 is the only one that fits this criteria as the grade points for ID -1 increased from 10 in 2009 to 20 in 2010. In my context it essentially calculates promotions in my dataset.

Thanks a lot for your help!