Help with time and date stamping entries

[Randy B]

I would like to automatically date stamp entries made on
an excel spreadsheet that will be used in pocket excel.

We have an inspector collecting tickets from trucks
delivering asphalt on a project. When the entries (truck
number and tons of asphalt), are entered on a PDA, I'd
like an additional column(s) automatically filled in with
time and date. My problem is that I haven't found a
function that "stamps" the current date once and then
fixes it so it doesn't change when the next truck delivery
is made.

This needs to work between a desktop running Win 2000
(Excel 97) and a PDA with PPC 2002 (pocket excel)