There are alternatives to using the pageup/pagedown keys, if you handle the scrolling yourself you could use any function key for the scrolling.
I’m not sure what you mean by scrolling “automatically” – do you mean moving to the next subfile page after selecting the last record on a page?
Are there any examples of commands or programs in the OS which do what you want to do?
If you want automatic page-scrolling, don’t use subfiles. Use the DSM APIs. Or even easier, use COBOL’s WRITE with a ROLLING phrase.