I need an updated excel 2007 formula

I am using the following formula:

=SUM(IFERROR(INDEX('[Report1.xls]Sheet1!$AX$14:$AX$1000,MATCH(B8,'[Report1.xls]Sheet1!$P$14:$P$1000,0)),0),(IFERROR(INDEX('[Report1.xls]Sheet2!$AX$14:$AX$1000,MATCH(B8,'[Report1.xls]Sheet2'!$P$14:$P$1000,0)),0)))

It works just like I need it to. However, the problem I am having on the production sheet is that since it references an accounting code and returns the percentage, there are some situations where that accounting code is used more than once and it returns a percentage value for the sum of the percentages. What would be a simple way to add to the formula IF the value returned is greater than 100% (or 1), it gets subtracted out?

For example: the above formula returns 188%. It should only be 88%

The above formula returns 200%. It should only be 100%