This standard call-back is used with %eb and takes a character string argument
containing a file pattern (e.g. '*.TXT'). A second character string argument
(called fname say) is required for the resultant file name (of size
129). A standard Windows 'file open' dialog is displayed and the resultant file
is written to fname. The file is then displayed in a %eb edit box that
is included in the current format window, replacing any text already there.
This standard call-back must only be used in a format window containing one and
only one %eb edit box. The corresponding edit box is usually supplied with a
buffer length of zero when it is set up, so that the system allocates the
buffer and adjusts its size as necessary. An example program appears in
A simple text editor.