Returning the sum of a range based on specified criteria

Hi all - Please find the attached sample workbook. What I'd like is for the user to select a month in C2 on the 'Report' sheet and to have cells c4:c8 reflect the sum for the corresponding month of the categories starting with the letters in the cells in b4:b8.

I realize that the easiest way to do this is to create a few more rows on the 'Date' sheet and to use a sumif formula (sumif($b$2:$b$68,"RU"&"*",c$2:c$68) for categoies starting with RU in January, fo example), and then do a vlookup on the Reports page, but I'd like to do away with creating more rows in the 'Date' sheet if possible.

I'm thinking that one way would be to utilize sumif, with the range rows pre-defined but the columns based on the month.
=SUMIF('Data'!$B$2:$B$68,"RU"&"*",'Data'!"<row based on month>"&"$2:<row based on month>"&"$68)
What I'd need is to make this work is a formula which would look up the month's name in cell c2 on the 'report' sheet and return the column letter of that month in the 'data' sheet.

If this is too complicated, I'm also open to other, simpler ideas as to how to accomplish this! Thank you.

Adam