two select commandfields in a gridview

[SR]

Hi,
if I want to put two select commandfields in a gridview like below, how can
I find which one was clicked in the SelectedIndexChanged event ?

<Columns>
<asp:CommandField ButtonType="Link" SelectText="Choose"
ShowSelectButton="true" />
<asp:CommandField ButtonType="Link" SelectText="Info"
ShowSelectButton="true" />
<asp:BoundField DataField="ContactName" HeaderText="Name" />
<asp:BoundField DataField="ContactCity" HeaderText="City" />
</Columns>

Thanks in advance
Sandro