[tex-eplain] pause?

[=?macintosh?Q?G=8Erald_Tenenbaum?=]

Hello,

Is there a way, with eplain, to define a macro, 
say \pause with the following effect:

\pause first develops as \vfill\eject
but after pressing some key (ideally the space 
bar or the next arrow key) on the key board, the 
command \vfill\eject is hidden.

Such a macro would be very convenient for 
lectures when you want to hide part of the 
displayed page.
Regards,

GŽrald