The filtering would have to be done within your Google spreadsheet before creating your map in MapAList.
One thought might be to have several worksheets in your Google spreadsheet - a master with all of your data, and then one for each month. You could then pull data from the master to the monthly worksheets and map each monthly worksheet individually.
Alternatively, assuming that you have month as one of the attributes associated with your addresses in your Google spreadsheet, you could create a map in MapAList that show all "things that happen" in January with red pins, all "things that happen" in February with green pins, etc. in order to show differentiation. Check out our tutorials for more info on this process at
http://mapalist.blogspot.com/2008/12/advanced-grouping-to-show.htmlHope this helps.