Data source name not found and no default driver specified

Sub AccessingSQL()
    Dim cn As New ADODB.Connection
    Dim rs As New ADODB.Recordset
    Dim SQL_String As String
    Dim StrConn As String
    Set cn = New ADODB.Connection
    StrConn="connectionstring"
    cn.Open StrConn
    Set rs = New ADODB.Recordset
    rs.Open Source:="PlanetaryOrbits", ActiveConnection:=cn, _
        CursorType:=adOpenKeyset, LockType:=adLockOptimistic, _
        Options:=adCmdTableDirect
    rs.MoveFirst
    Do Until rs.EOF
       If rs!Index = "104" Then
           n=n+1
           Cells(n+1,"C")=rs!idp
           Cells(n+1,"D")=rs!JD
           rs.Update
        End If
        rs.MoveNext
    LoopCells(2, 2) = rs!idp
    Cells(3, 2) = rs!JD
    rs.Close
    Set rs = Nothing
    cn.Close
End Sub