Записать в ячейки третьего листа сумму значений соответствующих ячеек первого и второго

Sub P1()
Worksheets(3).Range("A1") = Worksheets(1).Range("A1") + Worksheets(2).Range("A1")
If Worksheets(1).Range("A1").Value <> 0 And _
        Worksheets(2).Range("A1").Value <> 0 Then
    Worksheets(3).Range("A1").Interior.Color = vbYellow
ElseIf Worksheets(1).Range("A1").Value <> 0 Then
    Worksheets(3).Range("A1").Interior.Color = vbRed
ElseIf Worksheets(2).Range("A1").Value <> 0 Then
    Worksheets(3).Range("A1").Interior.Color = vbBlue
End If
End Sub

Sub Test()
    Dim s01 As Worksheet, s02 As Worksheet, s03 As Worksheet
    Dim i As Long, j As Long, m As Long, n As Long
    
    Set s01 = ThisWorkbook.Worksheets(1)
    Set s02 = ThisWorkbook.Worksheets(2)
    Set s03 = ThisWorkbook.Worksheets(3)
    
    'm = IIf(s01.UsedRange.Row + s01.UsedRange.Rows.Count > s02.UsedRange.Row + s02.UsedRange.Rows.Count, s01.UsedRange.Row + s01.UsedRange.Rows.Count, s02.UsedRange.Row + s02.UsedRange.Rows.Count) - 1
    If s01.UsedRange.Row + s01.UsedRange.Rows.Count > s02.UsedRange.Row + s02.UsedRange.Rows.Count Then
        m = s01.UsedRange.Row + s01.UsedRange.Rows.Count - 1
    Else
        m = s02.UsedRange.Row + s02.UsedRange.Rows.Count - 1
    End If
    
    'n = IIf(s01.UsedRange.Column + s01.UsedRange.Columns.Count > s02.UsedRange.Column + s02.UsedRange.Columns.Count, s01.UsedRange.Column + s01.UsedRange.Columns.Count, s02.UsedRange.Column + s02.UsedRange.Columns.Count) - 1
    If s01.UsedRange.Column + s01.UsedRange.Columns.Count > s02.UsedRange.Column + s02.UsedRange.Columns.Count Then
        n = s01.UsedRange.Column + s01.UsedRange.Columns.Count - 1
    Else
        n = s02.UsedRange.Column + s02.UsedRange.Columns.Count - 1
    End If
    
    For i = 1 To m
        For j = 1 To n
            If s01.Cells(i, j) <> 0 And s02.Cells(i, j) = 0 Then
                s03.Cells(i, j) = s01.Cells(i, j)
                s03.Cells(i, j).Interior.Color = vbRed
            ElseIf s01.Cells(i, j) = 0 And s02.Cells(i, j) <> 0 Then
                s03.Cells(i, j) = s02.Cells(i, j)
                s03.Cells(i, j).Interior.Color = vbBlue
            ElseIf s01.Cells(i, j) <> 0 And s02.Cells(i, j) <> 0 Then
                s03.Cells(i, j) = s01.Cells(i, j) + s02.Cells(i, j)
                s03.Cells(i, j).Interior.Color = vbYellow
            End If
        Next j
    Next i
    
    Set s01 = Nothing
    Set s02 = Nothing
    Set s03 = Nothing
End Sub