Here is some code to find a control inside a footer on the rowdatabound event..in this example they find a ddl....obviously you are looking for a differnt control...and doing something when you find it..but same concept.
if (e.Row.RowType == DataControlRowType.Footer)
{
GridViewRow row = grdValidations.FooterRow;
Control ctl = row.FindControl("drpdnFieldName");
DropDownList ddl = ctl as DropDownList;
if(ddl != null)
{
//you can do what evey you want to do with the dropdownlist here
ddl
}