Focus On A Input Field

I've written the following function who works great in IE

function OnlyCharacter(tekst)
{
if (tekst.length == 1)
{
if (tekst >= "A" && tekst <="Z")
{return true}
}
window.alert ("Only uppercase");
form1.Sectie.focus();
}


But in Netscape or Mozilla I can't bring back the focus on the field
(Sectie) when the input is not correct

I've tried the following :


1) var box;
box = document.forms[0].elements[1];
box.focus()
2)document.getElementById("Sectie").focus();
3) document.form1.Sectie.focus()

but nothing seems to work.

How must I do that in Netscape and/or Mozilla?