Assuming that you have not set your list box as a multi-select list box, and assuming that the "Plant No" field is the bound column in your list box, you can use code in the After Update event of your list box like:
Code:
Me.NameOfYourTextbox = Me.NameOfYourListBox
Just change the "NameOfYourTextbox" and "NameOfYourListBox" to the actual names of your textbox and listbox appropriately.
The columns in a listbox or combo box have a zero based numbering. This means that you can refer to any column in a listbox or combo box (visible or not) with code. To refer to the second column you can use code like: