an example can be found on AMOSPro_Tutorial:Tutorials/Interface/Editing_zones.AMOS
Returns a piece of text assigned to a zone. If your chosen zone doesn't actually contain any text, you'll be presented with an empty string "".
channel is the number of a currently open Interface channel
zone specifies the button or zone to be tested.
If you omit the version number, RDIALOG will return the contents of the FIRST object you've defined with the present zone number.