Hi dgf,

Open Formulate, select your model and choose to create a new List.

Drag the "Union" block form the "Derive" menu on to the canvas, you will by default get two branches to Union:

Select the "Add" menu, then drag the "Standard List" block onto the the first branch. Find your custom lists from the dimension concerned and select it. If you click on the Pyramid icon top left, you ill see the members of your list displayed in the Preview Panel top right.

Add another "Standard List" block to the other branch and select the other List to process:

Clicking on the Pyramid icon will display the Union of the two sets as a list of Members of that dimension. Any time in Pyramid the same Member is derived from two or more lists, Pyramid will resolve it to one, so we get a list of unique Members, even though duplicates may have come from both lists.

Save your combined list and away you go!

Hope that helps.

Ian