Checksums for Sysex Messages in Max/MSP, NEED OPRATORS?

I have a "musical instrument" patch creates scales mathematically. Since I can't send them directly to my Mac's AU Synth (I'm not smart enough, ok?) I take the MIDI route and send a bulk tuning dump message to Max Magic Microtuner. I can create the entire 408 byte message without a problem except for one thing; I can't get the checksum correct. MMM receives it anyway, but then I have to clear the "invalid checksum" warning every few seconds.
The rule for a Sysex checksum is this, you "XOR" the entire message, excluding F0, F7, and the checksum itself. The result is "AND'd" with F7 to give a 7 bit number. I found a max object by Peter Elsea called "LXOR" which processes the list of numbers, but I can't (apparently) find an object to do the "ANDing" correctly. I've tried the "&" object and the "|" object in Max/MSP but they don't do the right operation. Does anyone know how to do this?

Many thanks, Jawnypants