AVERAGE IF statement based on matching condition and date ranges

Hello folks.

I have created a spreadsheet which creates an average of feedback for trainers in a training company. The form adds up the feedback score into column L of the summary sheet and I have created a summary sheet which I want you use to calculate the average for each trainer.

I have cobbled together an array formula which creates the overallaverage for each trainer based on the named ranges entered via the form.

It looks something like this:

{=AVERAGE(IF(trainer='Summary Sheet'!A3,tots,""))}

Hoever I would like to create an average on a monthly basis. I was trying to create something along the lines of:

{=IF(and(date>39844,date<39874),AVERAGE(IF(trainer='Summary Sheet'!A3,tots,"")))}

But to be honest, I think I am way off.

Any ideas folks? Thanks

Simon