Forms :: Column Name Based On Value In Other Control

I have a form with a subform. The subform is a continuous form with two controls, both textboxes. The value in the second box is looked up in a table, where the column name is the value from the first box.

I tried a lot already, this code seems to work but only for the first value of the continuous form and is not refreshed when I click next record on the parent form:

Code:
Private Sub Form_Load()
'get the value from the first textbox
strLabelName = Me.LabelName.Value
'get the ProductID needed for WHERE clause from parent form
strProductID = Me.Parent.ProductID
'use dlookup
strLabelValue = DLookup(strLabelName, "tblProducts", "[ProductID] = " & strProductID)
'place the returned value in the second textbox
Me.Text5.Value = strLabelValue
End Sub

Is it possible what I want and how may I establish this?