====== Combining MUST and CANNOT ======

You can easily combine //CANNOT// and //MUST// rules to create more complex rules. For example, let’s assume that buyers of our //custom brochure// __must__ select __either__ //Matte Card Stock// __or__ //Glossy Card Stock// from the //Paper Stock// category when they choose //4-Color Printing// from the //Select Colors// drop-down. As mentioned earlier in this document, you can’t create a //MUST// rule for more than one selection. However, you can certainly accomplish the logic defined above by using a combination of rules. Here are the steps:

  * First, we will create a //MUST// rule applied to the //Paper Stock// category. That allows us to force the customer to select at least one item from that category if //4-Color Printing// is selected.
    * From the //If customers select//… drop-down, we will pick //4-Color Printing//
    * In the … //they must select// area, we will select the //Paper Stock// category
    * We will then click on //Add Rule(s)// to save this new rule. The summary page now shows.

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{{conflict_management:combining_rules.gif|}}

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  * Now we need to restrict the available choices. We can do this by editing the existing rule and using the //CANNOT// option. On the rules summary page, we click on //Edit// next to the rule that we just created.
    * In the … //they must select// area, we will leave the //Paper Stock// category selected.
    * In the … //they cannot select// area, we will choose the items of that category that should __not__ be available for selection. In our example, that means choosing //Economy Card Stock//.
    * Save the rule by clicking on the //Update Rule(s)// button.

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