solution
Private Sub cboBuyer_Change()
Dim i
Me.lbPartNumber.Clear
Dim lastrow As Long
lastrow = Sheets("MASTER DATA").Cells(Rows.count, "B").End(xlUp).Row
Select Case Me.cboBuyer.Value
Case "DANIEL"
With Me.lbPartNumber
For i = 1 To lastrow ' Rowcount
Sheets("MASTER DATA").Activate
If Cells(i, 8) = "DANIEL" Then
.AddItem Cells(i, 2)
End If
Next i
End With
End Select