Insert Time/Change Tempo

I inserted time in the middle of a song. The section prior to the insert is at 120 BPM. The section after the insert is also 120 BPM. I want the middle section of time I inserted to be a different tempo; in this case it's 45 BPM.



Here's my problem: when I change this middle section to the new tempo, all the subsequent tempos in the rest of the song are pushed farther down to different bars, even though I check "preserve tempo after selection".



What do I do to keep the other tempos I've set to stay in their place after changing a middle section? Thank you.