Sumproduct By Last (criteria) Month With Data

I have 3 or 4 criteria and one data range to sum based on these criteria. If I remove date as a criteria, I can make a sumproduct formula work, and even if I include a specific month it works as well, I would like to write a formula that uses the most recent month with data as a criteria. My reasons are that some banks pay our reps monthly, some quarterly, some semi-annually, and some whenever they damn feel like it. I need to take a snapshot of what each rep has invested in each bank: So for Bank A his last Statement came in March, but Bank B sent a statement in January. Here's what I have so far:

=SUMPRODUCT(Month('2007 Data'!$F4:F$97),'2007 Data'!$G$4:$G$97=Sheet1!$A2,'2007 Data'!$B$4:$B$97=Sheet1!$G$1,'2007 Data'!$H$4:$H$97)/(month('2007 Data'!$F$4:$F$97)

I know that the Month function here is incorrect but I'm going bonkers trying to wrap my head around this.

FYI, 2007 Data is my Data page, Col F = Date Range, Col G = the Rep ID, Col B, = the Bank name, Col H = Assets Invested; Sheet1 = my results page.

I know, I KNOW, many of you will scratch your heads and say this idiot should just use a Pivot table, I know. I have. Let's just say some of the end-users are not comfortable with Pivot Tables. I've come up with a simple listbox/command button to populate the axes of the chart (Column A = Reps, Row 1 = Banks)and I need this formula inside the chart.

After seeing and learning from many of the posts on this site, I'm sure someone knows how to acheive what I'm after, I think it's just a matter of my communicating it as well as I can.