Display the standard file Open dialog

subroutine OS_OpenDialog (string  : Primary_Window_Name,

                          string  : Title_For_Open_Dialog,

                          string  : File_Name,

                          integer : Error_Level)

Primary_Window_Name must contain the name of the program's primary region.

The Title string contains the text to appear in the dialog's title bar.

The path and name of the selected file is returned in File_Name.

Error_Levels are:

0        Normal completion; File_Name is valid.

1        User cancelled the dialog.

-1        Primary Window Name is invalid.

A standard All files (*.*) filter is used with this routine. If you need use different filters, then use the OS_Common_Dialog routine. This routine merely returns the fully qualified file name, it does not actually open or read the selected file.