Javascript not updating value in Input of Modal1 from Modal2

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C#

ASP.NET

Javascript

bootstrap

i have a page,where i am using bootstrap modal,

please find page architecture sample,

<pre lang="HTML"><mypage>
<repeater>
<a >triggers modalbox1</>
     <modalbox1>  
     <updatepanel>
      texbox
      <a>triggers modal 2</a>
      </updatepanel>
     </modalbox1>
</repeater>

<modalbox2>
<updatepanel>
<repeater>select button</repeater>
</updatepanel>
</modalbox2>
<mypage>

i want whenever user select an item from repeater in Modal2 , value should be updated in textbox of Modal1, i have tried following javascript

function setJobID(idcontrol)
    {

   
        var controlToSet =document.getElementById(       document.getElementById('txtHiddenID').Value);
        var mycontrol = document.getElementById(idcontrol);       
        controlToSet.Value = mycontrol.innerText.toString();
        alert(controlToSet.Value);       
    }

in the above code alertShows me correct value, but its not getting updated/displayed in textbox of Modal1,

Can anybody help me wit this?