I'm further now then before but stuck in verifying past Dec.
Any idea?
IIf(Sum(IIf(DatePart("m",[PaymentDate])>=5 And 7 Or DatePart("m",[PaymentDate])<=Month(Date())-6,1,0))=0,Null,Sum(IIf(DatePart("m",[PaymentDate])>=5 And 7 Or DatePart("m",[PaymentDate])<=Month(Date())-6,1,0)))
If I do -7...