Tempo Track problems on Editing Scoring for Video

Summing up … I need everything in Muiscal Mode because I’m working with Music, Bars & Beats. My problem is making a change (new tempo or time signature) in the middle of the project. As soon as i insert a new tempo in the middle it has (obvious) consequences on the rest of the tempo track.

I want to make changes to a part of the project without it affecting the rest.