The multi column data validation list gives you the ability to look up data using more than one criteria. By creating this, you don't need to go and select Product code in one column, White in the next column and Medium in another column to see that you have 10 in stock for example.
How to create a multi column data validation list in Excel - Sage City
www.sagecity.com > blog > excel-tips-tricks-list > posts > multi-column-dat...
Excel 2007 and above
1. Data tab / Data Validation module.
2. In the name text box : name the range as List.
3. Create a list of validations in E3 (Data/Validation, in Allow: select "List" in Source: type =List)
4. Open the Name manager: Formula tab/set name/Name Manager, select the name of the range (List)
Display Multiple Columns in a Validation List in Excel - Ccm.net ccm.net > How To > Software > Office Software > Excel
Creating the Drop Down List in Excel
1. Select the cell or range of cells where you want the drop-down list to appear (C2 in this example).
2. Go to Data –> Data Tools –> Data Validation.
3. In the Data Validation dialogue box, within the settings tab, select 'List' as Validation Criteria.
How to Make Multiple Selections in a Drop Down List in Excel trumpexcel.com > select-multiple-items-drop-down-list-excel