prevent expression from calculating for Months that have not yet occurred

[brf10043]

I have the table below where I am calculating a CW Count per Month my Expression is Count (Distinct [CW ID]). 

The second expression calculated the difference between the Rows of the CW Count column

Expression is  If(RowNo(TOTAL) = 1, 0, (Count (Distinct [CW ID])) - Above(Count (Distinct [CW ID])))

Question 1:  How can I prevent the CW Count from calculating for Months that have not yet occurred.  For example, I would want the table to end at March.

Question 2:  How do I prevent the Monthly Difference column from calculating when the CW Count row is 0?

This is what I would like to see.

[brf10043]

Thanks Sunny!