Take a look at gphoto i'm not sure ( and it's for unix like systems )
http://www.gphoto.org/doc/remote/
And only hack around which i know works is using usb-ir transmitter which send the signal used by a Canon Remote , u can check signals ( start , stop ) by usb-ir transmitters , receiving signal from Canon Remote then , send it whenever u want with-in your program
Edit
Seems someone else figure it out first
Need to record video with a DSLR using an SDK
Edit 2
Breezesys found a solution it's seems there is an undocumented command , but Chris breeze won't give the info up as u can see here
http://www.breezesys.com/DSLRRemotePro/help/index.html?video_capture.htm
some hex or reverse engineer guy should look into it :/
Edit 3
As long as out here people saying :
it's undocumented look into functions for yourself
Here is list Of Commands and Functions , also u can extract them for yout self with dll export viewer ,
DPPLibCom
DPPDLL
EDSDK
EdsImage
MLib
Ucs32P
Also out here some n@sty tools do n@sty things with dlls i hope u know those , cause naming them here is illegal