Using Office 2007 with Win XP;

I have a form designed in Excel for use by many different persons over a LAN.

In the past I have used a formula like the following to generate a unique form
number: =NOW()*10^7

This number is then formatted into a 12 digit value like: 3984-8374-2472
An auto open macro converts this formula to a value whenever a user opens a
form and it works very well. We have not had any duplicate form numbers
generated because it is clocked down to such a small fraction of a second.

The problem is, this new form being developed can have no more than 9
digits. If I alter my algorithm to say: =Now()*10^4
I find it very easy to generate two or even three forms having the same form
number, which will not work, since each form must never repeat a number.

Is there a chance anyone out there can help me out with an algorithm that
will work? BTW, the form can also use alphabetic characters. I'd really
rather NOT rely upon a centralized counter file or incrementing MS-Access
table if possible.

Thanks much in advance for any help/suggestions.