I NEED HELP WITH FORMATING A FIELD

[flashdofu]

I need to format this field into xxx.xxx.xxx-xx It's automatically
generated by the form.php page this is the code...

function
createInputFieldCPF($field_title,$input_type,$inpu t_name,$input_value,$inpu*t_size,$td_width)

{
//pre: all parameters are strings.
//post: creates in inputField based on parameters.
echo"
<tr bgcolor=$this->row_color>
<td width='$td_width'><font
color='$this->text_color'>$field_title</font></td>
<td><input type='$input_type'
onKeyPress=\"return(currencyFormat(this,'.','-',event))\"
maxlength='13' name='$input_name' value='$input_value'
size='$input_size'></td>
</tr>\n";
}
And this is the page that gets the fields...
$f1->createInputFieldCPF("<b>$lang->accountNumber:</b>
",'text','account_number',"$account_number_value", '24','150');
see the createinputFieldCPF, it asks the form.php for the field and
shows it....it works fine, but i need to make work in the format
xxx.xxx.xxx-xx