====== Adding a MUST rule ======

Let’s add another rule, this time using the “//MUST//” rule type.

Continuing our example, let’s assume that customers that wish to order a //16-page brochure// must choose //Wire Loop// from the //Binding Option// category. To create the new rule, we will follow these steps:

  * From the //If customers select//… drop-down, we will pick //16-Page Brochure// (8 sheets)
  * In the … //they must select// area, we will select //Wire Loop// from the first box (items) and leave the second box (categories) empty.
  * In the … //they cannot select// area, we will not make any selections.
  * We will then click on //Add Rule(s)// to save this new rule.

The rules summary page will now show:

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{{must_rule.gif|}}

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In the storefront, if you select //16-Page Brochure// from the //Number of Pages// category, the item //Wire Loop// is automatically selected from the //Binding Option// category. If you attempt to deselect it, ProductCart shows an alert box indicating that the item is required based on the first selection, as shown in the image below.

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{{required_alert.gif|}}

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