....what i mean is, how do i prevent a user from just leaving the cell
empty.

i have a list of countries in column A, and in column B i have created
a data validation list (of prices). but users can simply leave column
B empty if they wish to - how do i force them to 'pick' from the list?
hope this makes sense. thanks


column a column b (drop down list to choose from)
belgium
denmark
uk
etc