Not working in IE, but works in netscape - Validation problem

The following Javascript validates all of the input characters in NC, but only the first in IE. Very strange, any thoughts would be greatly appreciated. Thanks.

function valHrs(input)
{
var msg = "Invalid Input, Hours must be between -24 and 24";

var inHrs = input.value;
var min = -24;
var max = 24;
var RefString="1234567890.-";

for (var count = 0; count < inHrs.length; count++) {
var tempchar = inHrs.substring(count, count + 1)
if (RefString.indexOf (tempchar, 0)==-1) {
alert(msg);
input.value = "";
return false;
}

var num = parseFloat(inHrs)
if(num < min ¦¦ max < num){
alert(msg);
input.value = "";
return false;}

input.value = inHrs;
return true;
}
}