*missile on collision with wall(or object you want):
---missile set speed to 0
---missile set acceleration to 0 (if missile.acceleration>0)
---missile play animation "explosion" (play from beginning)
*missile on animation "explosion" finish:
---missile destroy
or
add new sprite with explosion only then
*missile on collision with wall(or object you want):
---missile spawn sprite"explosion" at imagepoint 0
---missile destroy
*"explosion" on animation finish: explosion destroy