Create Random Number To Be Automatically Generated As Default Value For Record ID

I've been building a CRM in Access that allows for creating profiles for our accounts. When we add a new account, I'd like an Account ID to automatically generate and look like this: CRMXXXXX where the X's represent a random number. I originally wanted to set the field as autonumber to just count up, but unfortunately I need to append this value to another sales database we have; you can't store the text "CRM" with an autonumber in a table.

Right now, all I've done is place an equation in the default value of a textbox I have on my 'Add Account' form. I then made the control source of the text box the Account ID field. My equation is as follows:

="CRM" & CStr(Int(Rnd(Now())*10000))

This appears to work, as it generates a value in the correct format. However, I've realized that each time I open the CRM, the random numbers start over again and I run into issues of trying to create a new record with the same ID as a previously created record. I assume I need to incorporate some sort of timestamp to it in order to change it.