You need to work differently.

Create the song in BB. Use RB to render the tracks. Then export them to a DAW where you can use audio editing features such as volume envelopes. That allows you to turn the fill instruments down or off when the vocal is happening.

Using that method is the easiest way that I have personally found. Once you learn how it's done, it's actually very quick and easy.

My DAW of choice is Cakewalk's Sonar. There's a bunch of others. And.... Real Band, which you have, is a DAW. It's got some downsides but it's fairly functional overall. Of course.... Cakewalk by Bandlab is free now so there;s that.

You can find my music at:
www.herbhartley.com
Add nothing that adds nothing to the music.
You can make excuses or you can make progress but not both.

The magic you are looking for is in the work you are avoiding.