---
url: /technical/using-model-variables.md
description: >-
  A model variable can be inserted into a set, provided its value is an element
  of the dimension whose set is being edited.
---

# Using Model Variables

A model variable can be inserted into a set with the **Insert Variable** instruction. The key and the value can be anything you like - what decides whether a variable is usable in a given set is its **value**: it has to be an element of the dimension whose set you are editing.

![The Variables page, annotated to show that the key can be any name while the value must be an element of the dimension](/dimension-variables.png)

In the list above, `Time.Current Month` holds the value `2022 - Jul`. That value is an element of the **Time** dimension, so the variable can be inserted into a set built on Time. Naming the key with a `Time.` prefix is a useful convention for grouping variables, but it is the value - not the key - that determines where a variable can be used.

The variable is picked up in a set through the **Insert Variable** instruction:

![The Set Instructions editor, annotated to show the Insert Variable instruction, the two Insert Next Member instructions, and the resulting three columns](/dimension-set-functions.png)

Here `Time.Current Month` resolves to `2022 - Jul`, and the two **Insert Next Member from: Month List** instructions after it extend the set to `2022 - Aug` and `2022 - Sep`. Because the starting point is the variable, the whole set moves forward on its own whenever the variable is updated.

See [Sequential Set Functions](/technical/sequential-set-functions) for more on the Next and Prior Member instructions.