I have now updated FB to work. All looks good. (need a bit of testing)
Two things I like to note the formula did at first end up as : {"If(iCVP==2,iCVP-1,iCVP+1)"} so that made a mess. so I used {If(iCVP==2,iCVP-1,iCVP+1)} and that works
And then creating a new Dynamic Property iCVP...