Unique random number on opening form for first time

[Ragonz355]

Have created a section in some code that opens a pre-existing form so that users can input new data. However I'm stuck at this point, basically there is a field in there called invoice number which they need to type in an invoice number (this can be anything, they just have to check it doesnt already exist)

What I would like to happen is when they click on "Add New Enquiry" a unique invoice number is generated and put into the field for them, is that possible?

Code to open the form is as follows

Private Sub cmdAddNewEnquiry_Click()
On Error GoTo Err_cmdAddNewEnquiry_Click
 
    Dim stDocName As String
    Dim stLinkCriteria As String
 
    stDocName = "Job"
 
 
    DoCmd.OpenForm stDocName, , , stLinkCriteria, acFormAdd
    Forms!Job!STATUS.Value = "ENQUIRY"
 
 
Exit_cmdAddNewEnquiry_Click:
    Exit Sub
 
Err_cmdAddNewEnquiry_Click:
    MsgBox Err.Description
    Resume Exit_cmdAddNewEnquiry_Click
 
End Sub

[Rabbit]

In the table design, set the field as an autonumber and set it to Random.