Tempo issue

I'm composing a small piece of music and so far it has two tempos, slow then lively. I added the lively tempo in the tenth or so measure. When I played it back, the music started in the lively tempo, even though I had slow attached to the first notes, but changed back to slow on the fifth measure when the trumpet comes it. When it hits the lively tempo, it changes speed as it should.

I want the beginning to be slow like it should be. Help?