Rampage ability effect + buff ailment on hit?

Trying to create an ability that uses stampede as a basis, and inflicts upon any unit hit by it disease and poison. What triggers should I go about using to detect that someone has actually been hit by one of the stampede's projectiles? Or, alternatively, would it be more effective to try and have the projectiles themselves attach the buff? How would I go about stacking the buffs/abilities on a stampede projectile so they'll use them on hit?

Thanks again folks.

i dont think its possible to attach the effect to the stampede units since its a graphic more then a unit.

but you may need jass to detect when a user is hit .