How to SET a variable in CASE statement..

Is there any way to set a variable within the 'THEN' clause in the statement you see below? 

I just want to increment a variable in this fashion 

@var = @var + 1 

I'm also open to inserting rows into a temp table to get a count that way as well..  I am just not sure how to pull it off.

I would need to do the same for about 30 other case statements as well.  

Example: 

CASE 
	WHEN (
			(
				SELECT sum(BreakerHours) / sum(DemoHours) * 100
				FROM #DMData
				WHERE Warehouse = @Wh
				) > (
				SELECT highvalue
				FROM #ThresholdData
				WHERE Threshold_TypeId = 9
				)
			OR (
				SELECT sum(BreakerHours) / sum(DemoHours) * 100
				FROM #DMData
				WHERE Warehouse = @Wh
				) < (
				SELECT lowvalue
				FROM #ThresholdData
				WHERE Threshold_TypeId = 9
				)
			)
		THEN (

				SELECT 'Weekly Average ' + '(' + LEFT(CONVERT(VARCHAR(10), '8/14/2013', 101), 5) + ' to ' + LEFT(CONVERT(VARCHAR(10), '8/20/2013', 101), 5) + ')' AS [TD]
					,cast(round(sum(BreakerHours) / sum(DemoHours) * 100, 2) AS NUMERIC(36, 2)) AS [TD]
				FROM #DMData
				WHERE Warehouse = 782
				FOR XML raw('tr')
					,Elements
				)
	ELSE ''
	END

Any help is really appreciated,

regards, -c