As Jack S indicated you cannot progressively alter the speed. But if you want to alter the playback speed of an entire clip (Event) the option is in Properties or Switches where you can type in your rquired play speed.
I need to fit the speed of video with differents speed of music.
Example: video 1 : My music is at 100 bpm. Video and music duration is 60 secondes. Video 2 : Music at 75 bmp. Music Duration is now 80 secondes (1.33 x 60 sec)
I need to indicate at Movie Studio to play the video at 75% of speed to match with music... The new duration will be 80 sec and the entire clip will play.
Following @EricLNZ's suggestion, perhaps one-by-one set the speed of each video event to match what you want to match your audio, and then render that on to its own video event and then import that rendered video event into your project to replace the original 'too slow' video.