Here is an example of my spreadsheet:

A B C D E
Expense Type Owner Qtr1 Qtr2
Paper O WB (15.0) (17.0)
Stone (5.0) 1.0)

Columns B & C, TYPE and OWNER, are drop down lists of valid Expense Types
and Expense Owners. I've used Data Validation to STOP if a selection isn't
made from the list. Columns D and E are data entry columns, with Data
Validation set at WARNING if expense isn't greater than 1. The settings are
Allow Decimal less than 1. However, the user may override the warning and
proceed with entering positive numbers. This is ok. However, I want to add
a restriction - if no selections of Type and Owner are made in columns B and
C, I want to add a STOP with a message - "Please enter Type and Owner before
entering Expense." In the example I've given, the expensex for STONE in Line
3 could not have been entered until Columns B and C had entries from the drop
down boxes. How can this be done? I have intermediate skills and am using
Excel 2003. Thank you in advance for any advice you can give.