Set a month as range based on single date in one cell

I have dates in a row formatted as month/year, i.e. April 2011(4/1/2011). I need a cell under this date to match the April 2011 date to the same month and year in a column on another sheet that has daily dates and select that whole month (April) as the range. Once that range it selected I need it to find a maximum value from the column 2 to the right. Thanks in advance for any help, Mike