function checkKonto()
    {
        tmp = document..kontonr.value;
        filtered = "";
        for (i=0; i<tmp.length; i++)
        {
            if (tmp.charAt(i) >= '0' && tmp.charAt(i) <= '9')
                filtered = filtered + tmp.charAt(i);
        }
        if (filtered != document..kontonr.value)
            document..kontonr.value = filtered;
    }

    function checkBLZ()
    {
        tmp = document..blz.value;
        filtered = "";
        for (i=0; i<tmp.length; i++)
        {
            if (tmp.charAt(i) >= '0' && tmp.charAt(i) <= '9')
                filtered = filtered + tmp.charAt(i);
        }
        if (filtered != document..blz.value)
            document..blz.value = filtered;
    }

    function checkKKNr()
    {
        tmp = document..kreditkartennr.value;
        filtered = "";
        for (i=0; i<tmp.length; i++)
        {
            if (tmp.charAt(i) >= '0' && tmp.charAt(i) <= '9')
                filtered = filtered + tmp.charAt(i);
        }
        if (filtered != document..kreditkartennr.value)
            document..kreditkartennr.value = filtered;
    }

    function checkKKgueltig()
    {
        tmp = document..kreditkartengueltigkeit.value;
        filtered = "";
        for (i=0; i<tmp.length; i++)
        {
            if (i == 2)
            {
            	if (tmp.charAt(2) != '/')
                	tmp = tmp.substr(0,2);
                else
                	filtered = filtered + tmp.charAt(i);
            }
            else
            {
                if (tmp.charAt(i) >= '0' && tmp.charAt(i) <= '9')
                    filtered = filtered + tmp.charAt(i);
            }
        }

        if (filtered.charAt(0) > '1')
            filtered = '0' + filtered;
        if (filtered.length == 2)
            filtered = filtered + '/200';
        if (filtered != document..kreditkartengueltigkeit.value)
            document..kreditkartengueltigkeit.value = filtered;
    }

    function checkGeburt()
    {
        geburt = document..geburt.value;
        filtered = "";
        for (i=0; i<geburt.length; i++)
        {
            if ((geburt.charAt(i) >= '0' && geburt.charAt(i) <= '9') || geburt.charAt(i) == '.')
                filtered = filtered + geburt.charAt(i);
        }
        if (filtered.charAt(0) > 3 || filtered.charAt(1) == '.')
            filtered = '0' + filtered;
        if (filtered.length == 2)
        {
            if (filtered.charAt(0) == '3' && filtered.charAt(1) > '1')
                filtered = filtered.charAt(0);
            else
            {
                if (filtered.charAt(0) == '0' && filtered.charAt(1) == '0')
                {
                    filtered = '0';
                }
                else
                {
                    filtered = filtered + '.';
                }
            }
        }
        if (filtered.length == 4)
        {
            if (filtered.charAt(3) > '1')
            {
                filtered =  filtered.substr(0,3) + '0' + filtered.charAt(3) + '.19';
            }
        }
        if (filtered.length == 5)
        {
            if (filtered.charAt(3) == '1' && filtered.charAt(4)>'2')
            {
                filtered = filtered.substr(0,4);
            }
            else
            {
                if (filtered.charAt(3) == '0' && filtered.charAt(4) == '0')
                {
                    filtered = filtered.substr(0,4);
                }
                else
                {
                    if (filtered.charAt(4) == '.')
                    {
                        filtered = filtered.substr(0,3) + '0' + filtered.charAt(3) + '.19';
                    }
                    else
                    {
                        filtered = filtered + '.19';
                    }
                }
            }
        }
        if (filtered.length > 8 && filtered.charAt(9) == '.')
            filtered = filtered.substr(0,9);

        if (filtered.length > 8 && filtered.charAt(8) == '.')
            filtered = filtered.substr(0,8);

        if (filtered != document..geburt.value)
            document..geburt.value = filtered;
    }