You could just use an unbound field. In the on current of the form, set the value of the field to the DLOOKUP value. Then you could edit it, and you make an after-update event on the field update the field in your table if you wanted.

So something like this, you'd need to add your where criteria and stuff.

Private Sub Form_Current()
    MyField = DLookup("Name", "CustomerT", "CustomerID=" & CustomerID)
End Sub

Private Sub MyField_AfterUpdate()
    If MsgBox("Do you want to update your table to " & MyField & "?", vbYesNoCancel) <> vbYes Then Exit Sub
    CurrentDb.Execute "Update MyTable Set FieldName=" & MyField
End Sub


The questions are WHY are you doing this, and WHAT do you want to do with that number?

But yeah, what Adam said is correct. :)

Have the user click a button to fill in the textbox with the DLookup value (with the button's Click event), otherwise the user needs to manually enter a value.  This can be done with a bound field too.  See picture below.

I work for a drywall contractor that uses subcontractors that are paid by piecework - the database calculates the pay a subcontractor is due.   The models table in the database lists the number of boards needed/unit price for each model for the various types of work the subcontractors do (framing, hanging, finishing).  There are times when the sub does not do all the boards and other times, out of the finishes available, it is either one finish or another (not both) even though the builder offers 2 types of finishes on a model (OP or L4)  to their customers, so that is the reason the user may need to change the quantity.  

Thanks to Adam for his suggestion - I must have done something wrong - I tried it on one field and the field is now blank.  I will post images of the code and a copy of one of the orders.

Thank you Kevin - that sounds like a good workaround.  I am not sure how to do that - could you give me more details please?  Thank you very much!

You use the button's On Click (<--- click here) event to write code that runs when the user clicks the button.  The code simply assigns the DLookup value to the textbox.