Calculate Rolling Average Cost From Two Dataset

I need calculating a rolling 3 month average cost from the two dataset below. Which is the 3 month Average of Dataset1 / Dataset 2.

Dataset 1:

SELECT(factAdmissions.ContractCode + '-' +factAdmissions.BenefitPlanCode) AS [Contract Code],
factAdmissions.AdmitCCYYMM,
ISNULL(sum(AmountPaid),0)As [Amount Paid]
FROM factAdmissions

[Code] ....

Dataset2:

Select

(factMembership.ContractCode+'-'+ factMembership.BenefitPlanCode) As Product,
EffectiveCCYYMM,
ISNULL(count(Distinct MemberId),0) As MemberCount
From factMembership
Where EffectiveCCYYMM >= '200701'

[Code] ....