Only recently discovered Max and have been trying to put together an editor for my Roland Varios8. Problem i've got is the checksum. The math is very basic: 1:Add the values together required 2:If value exceeds 127 then subtract 128 3:Subtract from 128 for the checksum. The 2nd part is my stumbling block. I have searched the forums and unable to find a method that actually works. The example i found below works until the input value exceeds 110 but then outputs negative values. Please excuse me if this has already been answered. Like i say i'm very new to Max. If someone could advice on which objects to use etc that be would be very much appreciated.

Help with Roland Sysex checksum