Set any of the following options in the Property inspector:
File Field Name specifies the name for the file field object.
Char Width specifies the maximum number of characters you want the field to display.
Max Char specifies the maximum number of characters the field will hold. If the user browses to locate the file, the filename and path can exceed the specified Max Chars value. However, if the user attempts to type in the filename and path, the file field will only allow the number of characters specified by the Max Chars value.