I've figured this one out. Sort of.

Step one: use a Mac.

Step two: Copy the cells you want. Hit escape, so that the source range is no longer surrounded by a marquee. Now go to where you want the cells to go, and do Edit Paste Special ..., and specify VALU. Lo and behold, your formulas are moved without updating.

Basically, what happens is that you trick Excel into treating the cell contents as text rather than formulae, so it doesn't try to get clever with them. Happily, it doesn't treat them like text to the extent of not interpreting them as formulae once they're in the sheet.

This is under Excel for Mac 2004. I've tried with Excel 2003 on the PC, but it seems that as soon as you clear the marquee, the cells disappear from the clipboard. There may be a way to do it, and it may work in other versions, i have no idea.