Would it be possible to shoot at 24 fps then switch to 30 to edit then output back to 24 using final cut express?

Not really. The trouble is, it's mathematically impossible. Complex "pull-down" where it makes most of the frames count for 1 but a few count for 2 needs to be performed and this cannot be done in FCP.

why wouldnt you just edit in 24?

FCE doesn't let you edit in 24 (something stupid). Also, thanks for ya know, shedding the light upon this for me. Many thanks.

Peace

Actually, there could be a away. If you live in Canada or the U.S. (otherwise I hope you're in Japan) and have acess to a TV, VCR and digital camcorder (which doesn't need to be the camera you shot your footage with), you may be able to change the frame rate pre editing. All televisions and video equipment in North America meet NTSC standards (National Television Standards Comittee), which makes 30 fps (60 fields/second) their universal standard. Therefore, if you shoot a film at 24 frames per second, plug it into the TV and record it to a digital device, then load it onto the computer, it should be at 30 fps. If your digital camcorder has pass through technology, then you wouldn't even need to waste a tape.

However, the quality will be reduced, as 24 frames need to be stretched across 60 fields (like titaniumdoughnut explained).

I've never tried this, but it's worth a shot if you're still stuck.