Can not fire Grid View RowEditing event in page load?

Hi ,
Can not fire Grid View RowEditing event in page load?
I have a grid view , select the grid line item from popup when click the image button which is located in header template. When click the select button in popup window , fill up the grid row and allow to edit the quantity text box. 
code
In page load
If Page.Request.Params("__EVENTTARGET") = "ctl00_popupField" Then
   AddHandler grdDOLineItem.RowEditing, AddressOf grdDOLineItem_RowEditing
End If
Protected Sub grdDOLineItem_RowEditing(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewEditEventArgs)
   'bind the grid view row
End Sub
Thanks in advance


shangar
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