C# - Retrive A Control In A Specific ROW In Edit Mode In A GridView?

I use asp.net 4 + c#,I have a GridView with many rows.When a User click the EDIT button in GridView I need to retrieve a Control in that specific row (now in edit mode).This Logic should work on GridEvent_RowUpdatingAt the moment my code (wrong) look inside every Row, so the Control founded is not unique and I receive an error.

// Event handler
protected void uxManageSponsoredContentsDisplayer_RowUpdating(object sender, GridViewUpdateEventArgs e)
// My code (Wrong!!!!):
foreach (GridViewRow row in uxManageSponsoredContentsDisplayer.Rows)
{
TextBox uxStartDate = (TextBox)row.FindControl("uxEffectiveStartDateInput");
}

Hope my question is clear. Solution:

TextBox uxStartDate = (TextBox)uxManageSponsoredContentsDisplayer.Rows[e.RowIndex].FindControl("uxEffectiveStartDateInput");