Private Sub Worksheet_Calculate()
Application.EnableEvents = False
Range("BF3") = Range("BF1") - Range("AR12")
Application.EnableEvents = True
End Sub

Private Sub Worksheet_Change(ByVal Target As Range)
Application.EnableEvents = False
If Target.Address(0, 0) = "BF1" Then Range("BF3") = Target.Value - Range("AR12")
If Target.Address(0, 0) = "BF3" Then Range("BF1") = Target.Value + Range("AR12")
If Target.Address(0, 0) = "AR12" Then Range("BF3") = Range("BF1") - Target.Value
Application.EnableEvents = True
End Sub

Private Sub Worksheet_Change(ByVal Target As Range)
If Not Intersect(Target, [A:C]) Is Nothing And Target.Count = 1 Then
     Application.EnableEvents = False
     cl = Target.Column
     rw = Target.Row
     If cl <> 1 And Len(Cells(rw, 2).Value) And Len(Cells(rw, 3).Value) Then _
         Cells(rw, 1).Value = Cells(rw, 2).Value + Cells(rw, 3).Value
     If cl <> 2 And Len(Cells(rw, 1).Value) And Len(Cells(rw, 3).Value) Then _
         Cells(rw, 2).Value = Cells(rw, 1).Value - Cells(rw, 3).Value
     If cl <> 3 And Len(Cells(rw, 1).Value) And Len(Cells(rw, 2).Value) Then _
         Cells(rw, 3).Value = Cells(rw, 1).Value - Cells(rw, 2).Value
     Application.EnableEvents = True
End If
End Sub

Option Explicit

' переключение галки (отметка изменяемого параметра)
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
      With Target
          If .Cells.Count > 1 Then Exit Sub
          If Not Application.Intersect(Range("A1:C1"), Target) Is Nothing Then
              Application.EnableEvents = False
              Cells(1, 1).Resize(1, 3).Value = ""
              Application.EnableEvents = True
              Cells(1, .Column).Value = "ь"
          End If
      End With
End Sub

' подстановка формулы
Private Sub Worksheet_Change(ByVal Target As Range)
      If Target.Cells.Count > 1 Then Exit Sub
      If Not Application.Intersect(Range("A1:C1,A3:C3"), Target) Is Nothing Then
          Application.EnableEvents = False
          Cells(3, 1).Resize(1, 3).Value = Cells(3, 1).Resize(1, 3).Value

          Select Case "ь"
              Case Cells(1, 1).Value
                  Cells(3, 1).FormulaLocal = "=B3*TAN(РАДИАНЫ(C3))"
              Case Cells(1, 2).Value
                  Cells(3, 2).FormulaLocal = "=A3/TAN(РАДИАНЫ(C3))"
              Case Cells(1, 3).Value
                  Cells(3, 3).FormulaLocal = "=ATAN(A3/B3)*180/3,14"
          End Select
            
          Application.EnableEvents = True
      End If
End Sub