CustomListInput

The custom list input control is like the custom link input control, however this control allows for multi-select.

Clicking the left button will start a library action, which lets the user select one or more record(s). 
After confirming the selection, the primary key of the record(s) is/are returned and the list is updated using these primary keys.

Clicking the right button will clear the selection.

Ctfp's

To use this control for a specific contenttype field, you must specify the ctfp cms:control and set its value to customlistinput.

Which library to open must be specified using the ctfp cms:actioncode. Its value must refer to an existing Useraction's code.
The caption of the button must be specified using the ctfp cms:buttoncaption.

The ctfp cms:lookupquery must be specified, so the control will be able to create a display value for the selected records.
Notice that the lookupquery should return Nr and Title. 

So, if the underlying table does have different column names, specify Nr and/or Title as alias.
Example: select Nr, Subject as Title from Tasks

These three ctfp's are required when the customlistinput control is used.