Make control inside grdivew visible

<script language="javascript" type="text/javascript">
function GetFileName(fileUp) {
var gv = document.getElementById("<%=gv.ClientID %>");
var gvRowCount = gv.rows.length;
alert("aa");
for (var j = 2; j < gvRowCount; j++) {
var filePath = fileUp.value;
c = gv.rows[j].cells[15];
document.getElementById(c.childNodes[1].id).innerHTML = filename;

}

return false;
}
</script>


In this Javascript,
gv.rows[j].cells[15] has 3 controls(textbox,label,imagebutton)

c.childNodes[1].id ->first control

i need to make 3rd control visible ->true

c.childNodes[3].visible=false (not working)