JavaScript TextBox Value Changes But Not Working in Server Side Effect

i am using GridView inbuilt textbox and enable disable true false and javascript calculation changes in value but grid view show proper sum but assign in server side not affect in textbox value.
server side first time assign value not changes pls help me 
Server Side Code :
 dr("iExpAmt") = Val(CType(gr.Cells(GV_Exp_TravelFare).FindControl("txtExpenseAmt"), TextBox).Text)
Client Side JavaScripts.
txtbox.rows[e.parentNode.parentNode.rowIndex].cells[9].children[0].value = TotalFare; CalcTotFare(e);


Advance Thanks,