It looks like you have a main form with a subform datasheet, but I don't see any list boxes - just what look like text boxes and there's a huge difference. If they're text boxes, the data in the sub form is supposed to be linked to whatever field you chose in the setup as the parent id of the record. The subform then displays the records related to the id on the main form if that's the parent field you chose to make the relationships between the two forms. The form navigation buttons down at the bottom left are used to move between main form records. If you're not seeing what you expect from this image, note that you have a filter applied (bottom of screen). So I don't see a need to navigate to a record below by double clicking on a text box. You should already be there based on the parent/child relationship between the main and subform recordsets. If you need to check this relationship, put the main form in design view, click on the subform control (it will highlight a box around the subform, but it is not the subform) and look at the data tab on the property sheet.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.