CoronaBitmap.filename no return?

Corona Corona for 3ds Max Help Required
1

I have a script running which assigns a selected HDRI to my Environment Background. At the end of the process, i want to show the filename of the Bitmap in the caption of the button. When i plug the HDRI into a normal bitmap, i can get the filename easily, but when a coronabitmap is selected, the .filename property isn’t returning anything? Anyone having a solution to this?

		on MPBTN_Environment picked texmap do
			(
				try
				(
					renderers.current.bg_texmap = texmap

					if (classof texmap == CoronaBitmap) == true then
					(
						print "Corona Bitmap"
					)

					if (classof texmap == Bitmaptexture) == true then
					(
						print "Bitmap"
					)

					texmappath = texmap.filename
					texmappath2 = pathConfig.stripPathToLeaf texmappath

					MPBTN_Environment.text = texmappath2

				) catch()