Average LAST 6 Values in a Column, based on criteria

Hi,

If I have A1=100 and A2=200

A5 to A60 could contain numbers between 50-300

How do I get an average of the last 6 values within the range A5:A60, but not include items less than A1 or greater than A2??

The values within A5:A60 could be between 50-300, or could be blank if the user not got that far, they will always add after the last number never leaving a gap.

Thanks