Yes, darnold was correct in stating that you will need a midi devie to sync your components together. Go to
http://www.midiman.net, purchase one of the Midisports (either the 2X2 or the 4X4, I'd say for U to get the 2X2, because you could slave the keyboard drum machine off of the 1680) USB.
There is also a "studioware" panel in Cakewalk for your 1680. You will probably have to do a search
this BBS for the link to the studioware panel (I know I posted it, but I can't remember where

).
Ok, you'll need to connect the USB midisport to your comp.
You will need to make Cake the MASTER device (generate MTC or clock) (I'm not sure which the 1680 uses).
You have to setup the 1680 to be the slave (receive MTC or clock).
And the same for your keyboard drum machine.
Make you MIDI connections like this...
OUT of the laptop, IN to the 1680. OUT of the 1680, IN to your keyboard drum machine.
p.s. You will still need to have more INS/OUTS for your laptop. You can use an expansion device from the same site as above
http://www.midiman.net
p.p.s. You will probably have to get a USB expansion device, because now you will need 2 USB ports
p.p.p.s. I have a much more info to share with you, but I have to go work on some music, so I'll post you back later on tonight.
peace...
spin