I think you have already received an answer, but in case anyone else with the same question finds this thread, the way to do this is to use the KF system() call.
For example, if you add an attribute in the KF navigator, give it a name, select Any for the type, and use this for the formula:
system("start /wait winword.exe");
Then it will launch Microsoft Word and pause until you close the Word window. The /wait is optional, I just used that to make it easy to tell what was happening. You can launch many different kinds of things this way.