I need a function which retrieves all the datas of a specific
field and add it to the listbox.?

This code below returns only the last data of the field :

Private Sub Cmd_onClick()
lstname.AddItem GetProdList()
End Sub

Public Function GetProdList() As Variant
Dim list As Variant
Set rsp = New ADODB.Recordset
rsp.Open "select * from product", cn, adOpenDynamic, adLockOptimistic
Do While Not rsp.EOF
list = rsp(0)
GetProdList = list
rsp.MoveNext
Loop
End Function

How do I proceed?
Note: I need to compulsorily use a function to do this.