In order to launch LANDesk's remote control from another application, you can just use this URL: http://<CORESERVER>/remote/RemoteSession.aspx?operation=rc&machine=<MACHINENAME>

There are a couple of potential gotchas...

• Authentication to the URL. That URL is  inside the LANDesk web console and consequently is dependent on NTLM authentication to the core's web service. If you have Internet Explorer as the default browser and integrated authentication is turned on and you're logged into windows as a user with rights to use remote control, it will just work; everyone else is going to get an authentication popup. Enter the proper credentials in domain\user form and you'll be fine.
• Authentication to the controlled computer. Depending on how you've set things in Agent Configuration > Remote Control, you may or may not need to authenticate further. The various levels of security are too complex to go into here, but the short answer is that if you're using NTLM, Certificate, or Integrated and you are logged into Windows as a user without rights in LANDesk, you'll be presented with another authentication prompt. You may need to be quick, I've sometimes had to re-initiate the connection after typing in accurate information, but too slowly.