Personally I'd use types for each of the objects you want to animate, and as well as other fields like their co-ordinates and movement speeds and whatnot I'd have a field for their last animation time, and their current animation frame. Add to that a constant (for each different kind of object) that defines how quickly they animate (how many milliseconds delay between frames, that is).
Then, when you update your objects in the main loop, you would (for each of them) subtract the last anim time (set with Millisecs() the last time it advanced a frame) from the current Millisecs(), and if the difference is equal-to-or-greater-than the animspeed constant you set, then tell it to
1) advance to the next frame, (probably) looping back to the first if need be (use the mod command for that)
2) set the last anim time to be the current Millisecs()
That should do it.
Then, when you update your objects in the main loop, you would (for each of them) subtract the last anim time (set with Millisecs() the last time it advanced a frame) from the current Millisecs(), and if the difference is equal-to-or-greater-than the animspeed constant you set, then tell it to
1) advance to the next frame, (probably) looping back to the first if need be (use the mod command for that)
2) set the last anim time to be the current Millisecs()
That should do it.