Enter the required items and quantity in the external segment, but assign suppliers in the in-house planning segment.

1. Create an external   Order segment containing items.
2. Right-click on the order and select Add >  Internal planning segment .
   This option must be enabled by a user with administrative rights under  Administration >   General settings >  Events > Enable > In-house planning segments for all item types .
3. Click on   in the toolbar above the list of items to show the column Role/Supplier. The column is not available in all views.
4. Assign a supplier in the Role/Supplier column.
   Note: The staff role must be enabled for  Purchasing and have at least one active, linked  Supplier item with a price assigned to it.