With this intent you can create Skype Conference Chat with all user you want:
B4X:
Dim skypeId As String = "devil-app;pippo"
Dim collegati As String = "skype:" & skypeId & "?chat&topic=B4A%20Chat"
Dim skype As Intent
skype.Initialize(skype.ACTION_VIEW, collegati)
skype.SetComponent("com.skype.raider")
StartActivity(skype)