Sub insertBlankRows()
    
    Dim L As Integer
    Dim C As Integer
    Dim n As Integer
    Dim v As Integer
    Dim intervalo As Integer
    
    L = 1
 
    intervalo = InputBox(Prompt:="Digite o número referente ao intervalo desejado", _
    Title:="Inserir dado de inervalo", Default:="3")
  
  
    Do
      
      L = L + 1
      If Cells(L, 1).Value = "" Then Exit Do
      
      n = n + 1
      If n > intervalo Then
         For v = 1 To 3
             Rows(L).Insert Shift:=xlDown, CopyOrigin:=xlFormatFromLeftOrAbove
         Next v
         L = L + intervalo - 1
         
         For C = 1 To 12
             Cells(L, C).Value = Cells(1, C).Value
             Cells(L - 2, 8).FormulaR1C1 = "=SUM(R[-3]C:R[-1]C)"
             Cells(L - 2, 9).FormulaR1C1 = "=SUM(R[-3]C:R[-1]C)"
             Cells(L - 2, 10).FormulaR1C1 = "=SUM(R[-3]C:R[-1]C)"
             Cells(L - 2, 11).FormulaR1C1 = "=SUM(R[-3]C:R[-1]C)"
             Cells(L - 2, 13).FormulaR1C1 = "=SUM(RC[-5]:RC[-1])"
         Next C
         Range(Cells(L, 1), Cells(L, 12)).Font.Bold = True
         Range(Cells(L - 2, 8), Cells(L - 2, 13)).Font.Bold = True
         Range(Cells(L - 2, 13), Cells(L - 2, 13)).Font.Color = -16776961
         n = 0
      End If
    
    Loop
  
             Cells(L, 8).FormulaR1C1 = "=SUM(R[-3]C:R[-1]C)"
             Cells(L, 9).FormulaR1C1 = "=SUM(R[-3]C:R[-1]C)"
             Cells(L, 10).FormulaR1C1 = "=SUM(R[-3]C:R[-1]C)"
             Cells(L, 11).FormulaR1C1 = "=SUM(R[-3]C:R[-1]C)"
             Cells(L, 13).FormulaR1C1 = "=SUM(RC[-5]:RC[-1])"
             Range(Cells(L, 8), Cells(L, 13)).Font.Bold = True
             Range(Cells(L, 13), Cells(L, 13)).Font.Color = -16776961
             
End Sub

adGere,

Incrível! Obrigado pela aula de "como usar variáveis". Ficou perfeito.