append between udt files

I am in the process of putting my roof estimating program on a USB Flash drive that will transfer information to a Home PC. The flash drive will have most of the same programs as the desk top Home  PC. Both the USB & home pc have a UDT address book with same format.When i plug the USB into the main Home PC. How can add the the records  from the USB Address book to the desKtop address book and not have duplicates?
The UDT looks like this:
Private Type PersonalInfo
   
    stDate As String * 10
    stLastName As String * 25
    stFirstName As String * 20
    stStreet As String * 45
    stCity As String * 20
    stState As String * 3
    stZip As String * 12
    stPhone As String * 20
    stEmail As String * 35
    stDeleted As String * 1
    stWPhone As String * 20
    stCell As String * 20
    stPager As String * 20
    stFax As String * 20
    stNotes As String * 250
    stCompany As String * 25
    stCompanyOrLastname As String * 1 '(Flag to determine if saved by company name,supplier name, Personal name or last name)
  End Type

Dim gCustomer As PersonalInfo

The open looks like this:
 Open cusfile For Random As #miFilenumber Len = Len(gCustomer)
        If LOF(miFilenumber) / Len(gCustomer) > 0 Then
      For iIndex = 1 To LOF(miFilenumber) / Len(gCustomer)
      Get #miFilenumber, iIndex, gCustomer

The write looks like this:
Sub WriteRecord()
    Put miFilenumber, miIndex, gCustomer
   
    End SubStart Free Trial