You can use a line like this:
Me.ListBox1.ListIndex = 0
The first item in the listbox is item 0.
If you allow multiple selections, then this worked ok for me:
Option Explicit
Private Sub CommandButton1_Click()
Dim iCtr As Long
With Me.ListBox1
For iCtr = 0 To .ListCount - 1
If iCtr = 0 _
Or iCtr = 3 _
Or iCtr = 5 Then
.Selected(iCtr) = True
Else
.Selected(iCtr) = False
End If
Next iCtr
End With
End Sub
Private Sub UserForm_Initialize()
Dim iCtr As Long
With Me.ListBox1
.MultiSelect = fmMultiSelectMulti
For iCtr = 1 To 10
.AddItem "A" & iCtr
Next iCtr
End With
End Sub