In the properties of the control, scroll down to find "Double Click".
Click on the [...] to the right of that and select Code.
It will take you to the module. Enter the following, replacing formname with the form you want to take them to.
- DoCmd.OpenForm "formname",
I'm assuming you'll want there to be a condition based on the name that is displayed in the list box. To acheive this add the following.
- DoCmd.OpenForm "formname", , , "[yourfield] = Forms![yourform].yourcontrol"
formname = the form you want to open
yourfield = the field you want to base the criteria on
yourform = the form with the list box on
yourcontrol = the name of the listbox