How to diseable checkbox on selected index event of dropdown

function disableControls() {

 var e = document.getElementById("ctl00_ContentMFBackOffice_ddlSchemes");
 
 var strUser = e.options[e.selectedIndex].text;
  alert();
if(document.write(strUser.lastIndexOf("G")!=-1))
{
document.getElementById('chbReinvestFlag').disabled= 'true';
}
else
{
document.getElementById('chbReinvestFlag').disabled= 'false';
}
}

is it correct java script function

i want disable checkbox when string end with (G)
e.g  Tata(G)

Hi sagar,

Try this attachments,








Thanks
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