Excel automatic custom format conversion

[TooNice]

I was wondering if there is a way to automatically change one custom format to another across the entire worksheet or better yet, workbook?

I am in the process of translating a fairly comprehensive workbook from Japanese to English. The hard part (translating the content) is pretty much done, but for completeness sake, I still need to convert "＃百万円" to "¥＃M" (come to think of it "M" is the correct short form for "million" right?) etc.

I can do this manually by updating one cell, then select the other cells needing the same updates and apply the new custom format. It would take some time, but it's not a big deal, and I might miss some cells on the first pass (just because there are quite a lot), but it would get done eventually. But is there a more efficient method? [Edit: Ah, looks like Find & Replace work on custom format settings too]