I constructed a set of XL2000 worksheets to record my household utility
bills. They're named Power, Gas, Water, Sewage, and Garbage Pickup (GP).

Recently, I added another worksheet named Summary, and inserted the
function=SUM(Power:GP!B4) into the corresponding cell beginning. It worked
beautifully.

However, when I tried to apply the same function to an older (but still
XL2000) set of worksheets, it returns NAME?

Any ideas of why this function worked in one set and failed in the other?