Yes you can do this - but just bear in mind two things:
1) each Slingbox will require its own bandwidth. So make sure you have enough "upload" bandwidth at the location of the Slingboxes to cope with two video streams at the same time.
2) either Slingbox will be able to control the cable box so potentially you could both be changing channels etc at the same time.
You will basically set it up so that the cable box component output feeds the first M1's component input, and then the first M1's component output feeds the second M1's component input. Then the second M1's component output can feed the TV.