Sum across sheets with variable sheet names

[frankday]

My Spreadsheet has a tab for all 12 months. =SUM('Jan:Dec'!K25) works great. I want to copy that formula only have it use the sheet name where Dec is. Example: I want the sum of Jan:Jul on the July sheet and Jan:Aug on the August Sheet. But I don't want to have to change the formula on every sheet. So for that second value I want the formula to fill in the sheet name that that formula is on.

Thanks for your help.

 

[Artik]

You're going to get a little longer formula.

=SUM(INDIRECT("Jan:" & MID(CELL("filename", A1), FIND("]", CELL("filename", A1)) + 1, LEN(CELL("filename", A1)) - FIND("]", CELL("filename", A1))) & "!K25"))

Artik