How do you specify valid vs. invalid input when using Data Validation to create a drop-down menu in Excel (2013)?
For example, suppose you have a spreadsheet in which the range $C$5:$C$99 (named "Vendors") contains the names of several dozen vendors.
Then suppose after selecting a range of cells in a different column (intended to have drop-down menus), you input the following:
Data Validation > Settings > Allow > "List"
Data Validation > Settings > Source > "=Vendors"
At this point, how can you limit user-entries (in the cells with drop-down menus) to only the names shown in the drop-down list?
Also, under the 3rd tab (Error Alert) in the Data Validation window is a checkbox titled:
"Show error alert after invalid data is entered"
but how do you know or define what constitutes valid vs. invalid data?