You need to create child products each with its own value. To do this navigate to the product to which you need to add the values and go the the Product Information page. Scroll down until you see the Add a Child Product Button. Click these and enter the necessary details. In the screen shot below we can see there are three child products added to the main or parent product.
We need then create a custom field in Virtuemart to display these child products on the product details page of the parent or original product. Navigate to the Custom Fields section in Virtuemart and create a new Custom Field. Choose type as Generic child variant. Check the Cart attribute to yes.
We need then associate this custom field with the parent or original product we wish to add the custom values to.Navigate to the original product and select the custom fields tab.
You will see a dropdown box Custom Field Type. Choose the name of the Custom fields you created earlier. Save and close the product. Now navigate to that product in the frontend of your web site and you should see a dropdown with the choice of child product you created earlier.