you could create your own login control to do this, but I think your easier approach would be to expose the username value in a control and use that i.e

set the value in your module load event

sub page_load()
Dim objUserInfo As UserInfo = UserController.GetCurrentUserInfo
                     UsernameText.text=objUserInfo.DisplayName
end sub

expose it via a control, then use that control reference as a parameter.
<asp:label id="UsernameText" runat=server>
 <SelectParameters>
<asp:ControlParameter ControlID="UsernameText" PropertyName="Text" />
    </SelectParameters>