Does anyone know the formula for Monthly Recurring Revenue?

Currenty I use the following formula for NMAC (Net margin after capital).
NMAC = [NPV(MRR) + NRI
- NPV(DirectMRC) - Direct NRC
- NPV(OPEXMRC) - OPEX NRC
- NPV(CAPMRC)
- (NPV(MRR) + NRI) * 1.86%
-(NPV(MRR) + NRI - NPV(DirectMRC - Direct NRC) * 1.1%]
/[NPV(MRR) + NRI]