small business network

I have a business application in which it would be
beneficial to have 2-3 users using a single excel
worksheet to keep track of order status and update it
from their terminals. This would not be high volume
useage, but rather convenience over walking across the
room. It would be acceptable if 1 blocked the other from
posting while they were posting. What would be the most
economical way to accomplish this? My current machine is
windows 2000 and office.

Thank you in advance for your input.

Bob