Using TabOrder to identify controls

I have a UserForm with 12 TextBoxes the values of which I need to enter into a WorkSheet.

I have given these controls tab indexes from 0 to 11.

I have been trying, unsuccessfully, to write code that will do the transfer on the lines of:-

Sub Transfer()
  Dim RowNo As Integer
RowNo defined in code
With UserForm1
   For tabIndex = 0 to 11
      Sheets("Data").Range(Cells(RowNo,TabIndex).Value = .Controls.TabIndex.Value
  Next
End With
End Sub

I know that I could accomplish this by using a control name such as "TextBox" & i but this way is not available to me as it is being used already for another purpose.
I hope that somebody will be able to put me on the right path.
John

I have followed your suggestion and used the Tag property with code as follows:-

Private Sub LastBt_Click()
Dim Ctrl As Control
Dim ComplaintNo as Integer
Dim RowNo As Integer
With Sheets("Customer_Complaints")
   ComplaintNo = Application.WorksheetFunction.CountA(.Range("A:A")) + 1
   RowNo = ComplaintNo + 8
End With
With EntryFrm
   
             For Each Ctrl In .Controls
                
                  For a = 0 To 11
                         If Ctrl.Tag = "Tag" & a Then
                        
                             Ctrl.Value = Sheets("Customer_Complaints").Range(Cells(RowNo, a + 1)).Value
                              
                         End If
                    Next a
            Next Ctrl
 End With
 Me.Hide
  EntryFrm.Show
End Sub

All works well till Ctrl.Value = Sheets("Customer_Complaints").Range(Cells(RowNo,a+1)).value
This gives an Application defined or Object defined error. Ctrl.Tag is what I expected, but I suspect that Ctrl.Value might be wrong.Can anyone help please?
John