Well if you absolutely want to have an ext3 partition on the drive (you still haven't told us why), you could do so by creating a large 4 GB loopfile on a FAT32 partition and formatting it as ext3.

I could go into more detail but I need to know what is the intended use. Is it for use on a single system or to carry around a lot? The reason is that loopfiles are not transparently mounted.