Hi JM,

You can use Data Validation in Excel to check if the ordered quantity is always a multiple of 12. Here are the steps:

1. Select the cell or cells where you want to apply the validation.
2. Go to the Data tab in the ribbon and click on Data Validation.
3. In the Data Validation dialog box, select "Custom" from the "Allow" drop-down list.
4. In the "Formula" field, enter the following formula:
   Formula:

   =MOD(A1,12)=0 

   (assuming that the cell you want to validate is A1).
5. Click on the "Error Alert" tab and enter a suitable error message, such as "Please enter a multiple of 12".
6. Click OK to close the dialog box.

Now, whenever someone enters a quantity in the selected cell(s), Excel will check if it is a multiple of 12. If it is not, an error message will appear.