Difference between Columns dynamically

[JVolk]

Looking for a measure formula to dynamically calculate the difference between Qtr 3 and Qtr 4.  

[Greg_Deckler]

Are Qtr 3 and Qtr 4 columns or measures?

If they are measures, you could just do:

Measure = [Qtr 4] - [Qtr 3]

If they are columns, then are these being summed or is there some other aggregation going on? Whatever the aggregation (let's assume SUM) then it would look like:

Measure = SUM([Qtr 4]) - SUM([Qtr 3])

Otherwise, there is not enough information to properly articulate a solution.

[JVolk]

Sorry I should have been more specific. My columns are date fields summarized by quarter.

[Greg_Deckler]

So how are you getting a whole number value from a Date field? Can you post some sample data?

[JVolk]

The Values are a count of completed demos, while the columns are the overviews scheduled by quarter.

[JVolk]

For clarification I am counting any row where the date field (overview_scheduled_at__c) is in quarter 3 and quarter 4 displayed as columns.  here is the data: