VBA emulates lag really badly, 1 frame of lag can turn into 5 seconds of time loss (RTA-wise i mean), if not more.

I recommend using Bizhawk instead, it's way better, mostly because it emulates GBA better than VBA does in general. Especially lag.

If DrHelix's response doesn't work for you, this question may be better asked in the MZM forums directly. Good luck.