Particle Bounce, Need some Help

Ok, I wrote a really simple particle engine, and I ran into a little snag with making the particles rebound. I tried using the generic bouncing code from the code archives, but I'm not quite sure how to blend it with my code...Here's the particle code I wrote. If anyone can tell me how to add rebound to it I'll be very grateful.

(Note sure how to do a code box...sorry)

Type Particle
Field Entity,XSpeed#,YSpeed#,ZSpeed#,Alpha#,Lifespan
End Type

Function CreateParticle.Particle(X,Y,Z,Sprite,Lifespan=100,R=255,G=255,B=255)

p.Particle = New Particle
p\Entity = Sprite
p\XSpeed = 0
p\YSpeed = 2
p\ZSpeed = 1
p\Alpha = 1
p\Lifespan = Lifespan
EntityType(p\Entity,CT_PARTICLE)
EntityColor(p\Entity,R,G,B)
PositionEntity(p\Entity,X,Y,Z)
RotateEntity(p\Entity,0,Rand(360),0)
Return p

End Function

Function UpdateParticles()

For p.Particle = Each Particle
MoveEntity(p\Entity,p\XSpeed,p\YSpeed,p\ZSpeed)
p\YSpeed = p\YSpeed - 0.1
If p\Lifespan > 0 Then
p\Lifespan = p\Lifespan - 1
Else
If p\Alpha > 0 Then
p\Alpha = p\Alpha - 0.1
EntityAlpha(p\Entity,p\Alpha)
Else
FreeEntity p\Entity
Delete p
EndIf
EndIf
Next

End Function

I don't need anything too fancy, just basic bounce for stuff like spent brass and debris...that sort of thing. No need to be mathematically correct or anything, just needs to look good.

Well, for a simple bounce off the ground, just invert the y speed and decrease it all the time :)

That would be great, except I don't know how to find out when the particle hits something that should invert it (like the floor). Y of 0 is not the universal floor in my project...

With a particle system it is probably best not to use collisions as that will slow things down. You could add a floor parameter to your particle system so if a particle goes below a certain value then reverse the Y velocity and multiply it by somthing smaller than 1 (say 0.95) to make it lose energy.