H o l a :
Te facilito la macro
Private Sub ComboBox1_Change()
'Fuente Dante
ListBox1.Clear
If ComboBox1.ListIndex = -1 Or ComboBox1.Value = "" Then Exit Sub
'
Set h1 = Sheets("Hoja1")
For i = 2 To h1.Range("A" & Rows.Count).End(xlUp).Row
If h1.Cells(i, "A") = ComboBox1.Value Then
ListBox1.AddItem h1.Cells(i, "B")
End If
Next
End Sub
Private Sub UserForm_Activate()
'Fuente Dante
'Carga el combo1
Set h1 = Sheets("Hoja1")
For i = 2 To h1.Range("A" & Rows.Count).End(xlUp).Row
agregar ComboBox1, Cells(i, "A").Value
Next
End Sub
Sub agregar(combo As ComboBox, dato As String)
'Fuente Dante
For i = 0 To combo.ListCount - 1
Select Case StrComp(combo.List(i), dato, vbTextCompare)
Case 0: Exit Sub 'ya existe en el combo y ya no lo agrega
Case 1: combo.AddItem dato, i: Exit Sub 'Es menor, lo agrega antes del comparado
End Select
Next
combo.AddItem dato 'Es mayor lo agrega al final
End Sub
Me comentas y valora para finalizar saludos!!