I'm trying to execute a stored procedure via Sharepoint's DataFormWebPart by passing it the currently logged in sharepoint username (a server variable essentially), however, I'm getting stuck on how to pass server variables. 

Here is what I have as code

```
<asp:SqlDataSource runat="server" ProviderName="System.Data.SqlClient" ID="SqlDataSource7" SelectCommandType="StoredProcedure" ConnectionString="xxx;" SelectCommand="xxx" __designer:customcommand="true">
    <SelectParameters>
         <!-- Not sure what to do here -->
    </SelectParameters>
</asp:SqlDataSource>

```

I know I want to do something like

```
<ParameterBinding Name="UserID" Location="CAMLVariable" DefaultValue="CurrentUserName"/>

```

But it seems I can only use asp parameter tags...