Average of 3 pieces of data from within a row

So I'm working on building an automated score sheet for a team.

I'm currently using the formula

=ROUND(AVERAGE(INDEX(B2:M2,LARGE(IF(B2:M2<>"",COLUMN(B2:M2)-COLUMN(B2)+1),3)):INDEX(B2:M2,MATCH(9.99999999999999E+307,B2:M2))),0)

To pull and average the latest three entries in each row.

The scores are needing to be based on a handicap system- the average of the previous 3 scores get subracted from the most recent and that number added to 1000, to find the handicapped score. Right now I'm using the spreadsheet to get the average, but it's also pulling from the most recent score, which is not desired.

For example,in the first four events in a season, a person scores A,B,C, and D. What I would like to have happen is to be able to enter the scores and have the spreadsheet automatically average the A,B,and C while saving the D for the overall handicapped score calculation.

My formula above is unfortunately taking the average of B,C,and D. Is there any way to have excel pull the 2nd most recent, 3rd most recent, and 4th most recent? Or possibly to have an exemption for the 1st most recent?