# Parameterised selections

## Create a parameterised selection

When creating a selection you may wish to mark certain parts of it that allow for user input. This could involve creating a complex selection with one or more elements that give the user the chance to determine the values used. For example a complex selection to determine a group of people might be further examined by their holiday destination. The User would then be prompted to choose the destination of choice with out being concerned with the rest of the pre-created selection.

In the above example the selection of Rich Professionals will have the holiday Destination element parameterised to allow other users to determine which Destination(s) they want to apply to this selection.

1. Right click on the variable to be parameterised and click on the option **Apply Parameters** from the pop-up menu.
2. The **Substitution Definition** window allows you to apply the required settings:

   **Substitution Type**

   - **Values**: This will give the user an option to select a category or enter a value.
   - **Variable & Values**: This will give the user an option to substitute the current variable with another from the same table.

   **Name**

   - This will be the description that the user will see. This can be amended here.

   **Prompt Title**

   - This will be the prompt description the user will see. This can be amended here.

   **Optional Substitution**

   - Ticking this box will activate the **Remove from selection** tick box on the Substitution Values window. This allows the user to ignore the parameterised part of the selection query.

   This example will use the default options. Click **OK** and notice that, in the logic tree, the parameterised variable is now shown in green and followed by a ?
3. Click on the **Build** button to be presented with the **Substitution Values** window, prompting you to select the relevant Destination(s):
4. Click the **OK** button to see the new result.
5. From the **Cover** page click on the **Substitutions** tab.

To use this selection again, you may want to set the **Behaviour** for how the user interacts with the selection:

- **Always Ask:** Any previously selected parameter(s) will remain checked, but every time the selection is used, the user will be prompted to see if a parameter needs to be changed.
- **Always Clear & Ask:** Any previously selected parameter(s) will be cleared and every time the selection is used, the user will be prompted to select a parameter.
- **Ask Once:** The user will only be prompted once to change the parameter.
- **Remove:** This option will ignore the parameterised part of the selection.

> [!NOTE]
>
> Due to the **Substitutions Behaviour** settings being held on the **Cover** page, a parameterised selection must be saved as a **Whole Book**.