Can you link tasks with contingencies?

Hi,

I'm curious to know how I could take a couple of tasks and link them so that one won't run unless the other is successful.  For example, I have a request to perform an uninstall or an old version of an application and then an install of the new one.  This is the only way the upgrade can be completed.  I want to create two tasks and link them so that the new version won't install unless the old version was successfully removed.  In my experience using Altiris and SCCM, this was possible.  I can't find a way to do it in LANDesk.  Where might I look, if anywhere?  I'm running version 9.0.3.2

Thanks!