[AccessD] I do not understand this

I built the following code using the autocomplete in the VB editor. Why
can't Access find the smpleSizeAll in the code?
 
Private Sub Detail_Format(Cancel As Integer, FormatCount As Integer)
    If Me.SmpleSizeAll.Value = True Then
    Me.txtSmplSize = "All Pieces"
        Else
    If Me.SmpleSizePieces.Value <> 0 Then
    Me.txtSmplSize = Me.SmpleSizePieces
        Else
    Me.txtSmplSize = "No Samples Needed"
 End If
 End If
 
    
End Sub