function AllowSubmit(sInputID, sSubmitID)
{
    if( IsNumeric(document.getElementById(sInputID).value) )
    {
        //IsNumeric=TRUE so ALLOW...
        document.getElementById(sSubmitID).disabled = false;
        return true;
    }
    else
    {
        //IsNumeric=FALSE so DISallow...
        document.getElementById(sSubmitID).disabled = true;
        return false;
    }
}

function IsNumeric(sText)
{
    var ValidChars = "0123456789.";
    var IsNumber=true;
    var Char;

    for (i = 0; i < sText.length && IsNumber == true; i++) 
    { 
        Char = sText.charAt(i); 
        if (ValidChars.indexOf(Char) == -1) 
        {
            IsNumber = false;
        }
    }

    return IsNumber;           
}