Slide dissolve units

I need some suggestions on slide projector dissolve units. I notice they go pretty cheap

these days on ebay and I want to use my 2 kodak projectors and hand-colored kodalith

slides to accompany music of friends who do club DJ'ing.

My needs at best are minimal, I could be happy with a unit that only fades between 2

projectors with a variable timer. However I could also get into the idea of setting up some

more complicated sequences, cuts whatever if there was a unit that would also do that. But

the timer is the most important feature I need.

One unit I am vaguely familiar with from years past is the Tiffen Pro-Dissolve. That lets

you program sequences via a cassette tape and inaudible tones on one track (if I am not

mistaken), the other track can be used for audio, which I won't be using. Does the Tiffen

also have a timer set-up? I haven't been able to find a manual online for this older unit.

I could also get something like an Entre 7640, which is timer only (I think).

Another thought would be to run them from my Mac Ibook. But I don't know of anything

device that would let me do that. There used to be something called an ADBIO that

plugged into the ADB port on ancient macs, and could be programmed with XCMDs. But

that wouldn't help me with USB or Firewire interface, even if I could find one.

Any suggestions or recommendations? I don't want to spend more than say $100 on this.