How to stop a pkg being updated to the latest with Apt

[Nigel Henry <cave.dnb@tiscali.fr>]

Apologies, as this question applies directly to my Fedora installs, where I've 
always used Apt. I also run Debian Sarge.Etch. and Lenny.

I don't expect any replies from the Fedora list, as Yum is the default package 
manager.

Anyway. This is the problem. I've had problems with ZynAddSubFX, and fltk. 
I've replaced the Fedora 8 version of fltk with the FC5 version of fltk, and 
now ZynAddSubFX is now working ok. Now though, if I run apt-get update, and 
apt-get dist-upgrade, fltk is going to be upgraded to the F8 version which 
doesn't work.

How do I prevent the fltk package being upgraded using Apt?

Apologies for asking a Fedora question on the list, but I do like Apt, and you 
guys/gals are the ones to ask.

Many thanks for all replies.

Nigel.