How to open a file dialog and return selected/new file as variable?

Hello,

i am using this expression to open a filedialog and return the selected path.

RunState.Engine.DisplayFileDialog("test","ok","c:\\",StationGlobals.S1,StationGlobals.S2,0,"",4100,"")

How can i enter a new filename in the selected path and return this value into the globals?

Thanks