I don't have C3 on my box anymore but I don't think you could animate metaballs with that version. You can for sure with C5. :-/ If you can animate in C3, you will need to do it while in the Metaball room using the timeline and keyframes. Upon leaving the metaball room, all theMBs behave as a single object in the Assembly room. At least that's how I do it in C5.