I've been doing the same, though I have not yet tried to separate by month. I do a summary by stakes that will show Net Gain, ROI, and ITM information.

As for your question, depending on how you have it formatted, (I'm assuming one sheet with a total at the bottom) I would copy each of the sheets so that you have a separate sheet for each month in the same in the same workbook. To do this, right click on the "tab" where the name of the sheet is (i.e. sheet1) and select "move or copy". You will get an option that will show all your open workbooks and select the one you want to move it to. Be sure to check the "make a copy" box, or it will remove the sheet from the old file.

Once this is done, right click on one of the tabs in your new yearly workbook and insert a new worksheet. Use the new blank sheet to create a summary that will show each month with an annual total.

Hope this helps!!

Great, thanks for the response. I will give this a shot when I get home from work tonight.