Sum if with Structured References for a Range

[mdrew9]

=Sumif(Table1[Criteria Column],Table2[[#this row],[criteria column]],Table1[[Dec-10]:[Apr-11]])

As you can see if the Range Dec - April meets the criteria that I want it should sum the range.
If I seperate this formula to just =sum(Table1[[Dec-10]:[Apr-11]]), it works fine. But once I introduce it to the Sum if it only adds up Dec-10. Running a pivot table on this criteria in Table 1 confirms that its only Dec-10 and not Sum(Dec-10 - Apr-11). Any ideas?

 

[mdrew9]

Additionally, if I convert this data set to a range and apply sumif I get the same incorrect result, if I apply sum(if()) array forumla I get the correct result.

 

[Yard]

A more efficient solution might be to have a column in your table which simply sums Dec-Apr. Then point your SUMIF at that column. Saves the need for array formulas etc.