Excel formula to build scorecard. Decimal values of a scoring grid.

I have designed a scorecard.
FY 2013 Goals
Parameter Weight 5 4 3 2 1
VOC 25% >=4.91 4.81-4.9 4.7-4.8 4.61-4.69 <=4.60
Case Closures 25% 7 6 5 4 3
ASA Critical 5% 100% 98% 95% 93% 90%

I can use the IF function like =IF(G3>=7,5,IF(G3>=6,4,IF(G3>=5,3,IF(G3>=4,2,1)))) to get the rating of 1 to 5. This is working well.

The help i need is to get the decimal values.
For E.g. if Case Closure is 5.5 the rating for that parameter should be a value between rating 4 and 3 and not default to 5

Hope i have explained what i am looking for.