number_format problem

I want to show a number from a database in the format x,xxx.00 in a textfield, then if it is changed by the user I want to post the value of the number to a decimal field. However, once you number_format the number it becomes a string, and numbers like 3,379.90 give a value of 3 when posted to the database, which is hinted at in the notes on number_format. I suppose I need a string to number function - can someone tell me what this might be called please? Regards, John                                            http://www.cantor.com CONFIDENTIAL: This e-mail, including its contents and attachments, if any, are confidential. If you are not the named recipient please notify the sender and immediately delete it. You may not disseminate, distribute, or forward this e-mail message or disclose its contents to anybody else. Copyright and any other intellectual property rights in its contents are the sole property of Cantor Fitzgerald. E-mail transmission cannot be guaranteed to be secure or error-free. The sender therefore does not accept liability for any errors or omissions in the contents of this message which arise as a result of e-mail transmission. If verification is required please request a hard-copy version. Although we routinely screen for viruses, addressees should check this e-mail and any attachments for viruses. We make no representation or warranty as to the absence of viruses in this e-mail or any attachments. Please note that to ensure regulatory compliance and for the protection of our customers and business, we may monitor and read e-mails sent to and from our server(s). For further important information, please read the Important Legal Information and Legal Statement at http://www.cantor.com/legal_information.html