Oh wow. Very different than I imagined. I'm very grateful for you telling me (and posting the screenshots)
So you're literally having to specify the parameters first (as Function.Param(number), and then adding the values later. I get it now.
And then, AFTER telling specifing the parameters you can then use On Function.myFunction(parameter1,parameter2), so for the MessageBox...
Messagebox.Param(1), MessageBox.Param(2), MessageBox.Param(3)
Add parameter xpos
Add parameter ypos
Add parameter message
Call function (And at this point on it works like a normal function)
Again, thank you so much.