RMVX - Character transforming during battle

I'm trying to give one character a skill to where he can transform in battle into another 'party member' (his alternate form.) I've gotten the skill in there, and he can use it...but the thing is that for some reason, it just starts automatically at the beginning of each battle. D:  No skill use necessary. 

Basically, I had two different actors made for him, his normal self and his beefy self.  I had made the common event which would remove him from the party and replace him with the beefy one, but yeah.  I also tried to do the same thing but using states instead, and it ignored using the change actor graphic.  D: 

Any help would be much appreciated! <3  I am using Yanfly's Engine Melody, if that matters at all.

Is it possible to see a demo?
or rather, just send as the data files and I'll see what I can do XD It's kinda hard to know from this stand point.

Sure, I will upload one in a bit, my bf has my laptop's internet at the moment, which is where my files are orz 

From the way you've written it I assume that you've used a battle event. If so, then there are two ways to do this.
1 - Make your skill call a common event, and make this common event activate a switch. Then, in your battle event, set the condition to run to "Switch [whatever your switch was] is ON" and make the character transform. Alternatively,
2 - Make the common event your skill calls do the transformation itself, applying conditional branches so that it can only be used in the appropriate battles. This method is better because you don't have to write it into every battle you want it in.
If you're not using a battle event, and just a common event, then follow method 2. Hope I've helped and not necroposted!
AP (HP).

I will give that a shot.  I'm so, so sooo sorry to Nessiah that I didn't post the demo D:  I was on my way back from Finland, and then things got really hectic when I came back to the states so I forgot about it >_< 

Well that's fine but if you want a better explanation over transformation:
http://rmt.divinelegy.com/tutorials/intermediate/transform.html
It has the same concept as VX so yeah. You can see more over here http://rmt.divinelegy.com/

Thank you very much~!  You guys rock!  :3