Adding Enter Button To Current Script

i want to integrate a Enter button with my following script...Rite now the script makes the user type in their password then click out side of the box for it the check the password and let the users in...And if they try to press enter it clears the password. Want it so the users can press enter and it can check the password and so the users can click enter to check the password and let them into the protected page...

<SCRIPT Language = "JavaScript">

function passwordOK(anystring) {
anystring = anystring.toUpperCase()

if (anystring == "XBOSFUN" || anystring == "XXX" || anystring
== "XX" || anystring == "X") {
location="coupons.html"
}

else {
alert ("Invalid Password.")
location="protected.htm"

}}
</SCRIPT>

<FORM>
<b>Password from NewsJournal AD: </b>
<INPUT type="password" name='pass' Size = 20

</FORM>