Private Sub UserForm_Initialize()
HI = TimeSerial(Planilha1.Range("B2"), 0, 0)
HF = TimeSerial(Planilha1.Range("C2"), 0, 0)
M = TimeSerial(0, Planilha1.Range("D2"), 0)
For I = HI To HF Step M
ComboBox1.AddItem Format(I, "hh:mm")
Next I
ComboBox1.ListIndex = 0
End Sub