Since you put it that way, Tony, I can help you.
What you are trying to do is count how much each bad win affected the RPI, and then subtract that. In stead of subtracting off the difference, you should just recalculate the average.
What you have to do is take .650*38 = Total of Game RPIs. (This number you have in your calculation already). Now, instead of trying to say (How much did Lindenwood affect this?), just subtract all the game RPIs that are below that .650, so .650*38 - .600 - .??? etc, until you have subtracted them all off. Let's call that ADJSUMRPI. The final total will be ADJSUMRPI/(#games-#subtractedgames). Your method will be slightly wrong because if there are 2 games, you are going to subtract some number like{(.650*38-.600)/37}-.650 + {(.650*38-.605)/37}-.650 where all the numbers you subtract have 37 for a denominator. But, the right answer has to have 36 in the denominator, because it is literally (RPI with bad games removed) which means, "Calculated without those games."
There is still one possibility of trouble. I am not sure how this would work, but it may be possible that you will miss a subtracted game or two. That is because the real definition of subtracted games is not "When Game RPI is lower than season RPI", but rather "When SUMGAMERPIs/SUMGAMES is less than (SUMGAMERPIS(-gameRPIinquestion))/(#games-1). So, what I mean is that you could have a situation where one game lowers the RPI by a lot, and one by only a little. When you average, using all games, the RPI calculated using all games may fall far enough that the game which would lower RPI by only a little isn't found by only looking at averages. For example, if the calculated RPI is .670, and one game has .570, that .570 will lower the total RPI by about .003. If some game has .671, that game maybe should be included, too. I am not sure. I don't know whether the 'remove games' thing is iterative or not.
Jim?