Apply An escalation rate depending on the year

graycrumbs First of all I assumed you had a typo and the you really wanted a compounding interest type on the escalation rate and therefore (1+escalation)^N, assuming escalation is a % increase since you are + base rate on top of it.  It isn't the prettiest and maybe one of you accountants know of some fancy accounting formula in excel to make it easier, but I believe it does what you want:

=LET(start,A2,end,B2,baserate,C2,escalation,D2,holidays,0,startyr,NETWORKDAYS(start,DATE(YEAR(start),12,31),holidays),endyr,NETWORKDAYS(DATE(YEAR(end),1,1),end,holidays),IFS(start>end,"bad start/end dates",YEAR(end)=YEAR(start),NETWORKDAYS(start,end,holidays),YEAR(end)-YEAR(start)=1,startyr+(1+escalation)*endyr,TRUE,LET(yrcount,SEQUENCE(YEAR(end)-YEAR(start)-1,,1,1),years,NETWORKDAYS(DATE(YEAR(start)+yrcount,1,1),DATE(YEAR(start)+yrcount,12,31),holidays),SUM(startyr,years*(1+escalation)^yrcount,endyr*(1+escalation)^(YEAR(end)-YEAR(start)))))*baserate)

you set the location of the start date (A2), end date (B2), base rate (C2), escalation rate (D2) and an array of holidays (0) you want to take into account.  you can play with it in the attached sheet.