afterFinish option not working as expected

Hello,

I'm trying to use the afterFinish parameter on the BlindDown effect,
but it's not working as I expect it to.  My function appears to be
called just as the effect is starting, not when the BlindDown is
complete (finished drawing).

Here's the code that I'm using for the most part...
Effect.BlindDown( mydiv, { afterFinish:Form.enable(myform) } )

Any ideas?

Thanks,
Andrew