Sumifs Formula using vlookup to chose which YTD calculation to use

I've got a spreadsheet with multiple years worth of sales data. I currently use a pivot table to gather the data for the current year and previous year so as to compare the two. On another spreadsheet I then do a vlookup on the pivot table based on the sales person's name. Every month I have to update all of my pivot tables to include the new month of data. I'm wanting to completely get rid of the pivot table version and go with something more like a Sumifs formula. This would make it much easier to maintain when going from one month to the next and one year to the next. I know I can do a =sum(sumifs...{"10","11","12"})) formula to sum months 10, 11 and 12. But I'm thinking what I might need (and I may be over thinking it) is to have a vlookup like this:

Col A Col B
Jan "1"
Feb "1","2"
Mar "1","2","3"....etc, etc

then I could have a drop down list where I choose the month and it returns the value in column B as in the above example. However, apparently I can't use a vlookup within {}. I've attached my example. Any help is much appreciated!Sumifs Example.xlsx

The reason I don't want to use a pivot table is because I have several pivot tables that summarize different data (sales people, product sold, key customers sold to, regions, etc). Usually they all have to be updated each month (but not always) and to do so all I do is update the pivot table to include the new month. It gets tedious updating each pivot table and it makes the file very large. I also don't like having a separate tab holding all of this information. I'd rather just build a formula directly in to my output worksheet. I'm pretty sure a Sumifs formula would do the trick. I just need a way of having the sumifs dynamically include the new month of data without me having to add to the formula each month.

I just figured it out!

=SUMIFS(C:C,A:A,"2014",B:B,">0",B:B,"<="&VLOOKUP(E11,$E$14:$G$25,3,FALSE))

where ">0" will be static and the vlookup is based on the value returned when the month is selected in the drop down (ie, Sep =9) therefore values >=0 and <=9 are returned.

Now I can just use this formula and it will update all cells automatically.