Private Sub UserForm_Initialize()
ComboBox1.AddItem Sheets("sheet1").Range("a1").Value
ComboBox1.AddItem Sheets("sheet1").Range("a2").Value
ComboBox1.AddItem Sheets("sheet1").Range("a3").Value
ComboBox1.AddItem Sheets("sheet1").Range("a4").Value
ComboBox1.AddItem Sheets("sheet1").Range("a5").Value
End Sub