Well that might be part of the problem, there is not a value in that cell. I am entereing in values into the rows from a userform. So there is no value in the order Number field to start with. This is what I was trying to get done in code. I did add the sheet name to your code and I am still getting the same error. I also tried adding DHORD into the cell and it also errored out. Code below

Private Sub Tset()
Dim RandomString As String, rgch As String
Dim Count As Long
Randomize

If Not Sheet1.Range("A1") = "" Then
Count = Right(Sheet1.Range("A1"), 5)
Count = Count + 1
Else
Count = 1
End If

    rgch = "abcdefghijklmnopqrstuvwxyz"
    rgch = rgch & UCase(rgch) & "0123456789"

    Dim i As Long
    For i = 1 To 5
        RandomString = RandomString & Mid$(rgch, Int(Rnd() * Len(rgch) + 1), 1)
    Next

Sheet1.Range("A1").Value = RandomString & Format$(Count, "00000")

End Sub
My Save Code - doing some other testing as well, so the call to this proc is commented out at the time

Private Sub Save_Click()
          
       lastrow = Range("C" & Rows.Count).End(xlUp).Row
        
        Range("A" & lastrow + 1).Value = "DH" + "0"
        Range("B" & lastrow + 1).Value = TTNum.Text
        Range("C" & lastrow + 1).Value = Req.Text
        Range("D" & lastrow + 1).Value = ReqD.Text
        Range("F" & lastrow + 1).Value = DH.Text
        Range("G" & lastrow + 1).Value = DHNum.Text
        Range("H" & lastrow + 1).Value = DHCst.Text
        Range("R" & lastrow + 1).Value = Rsn.Text

        'Tset
        
        MsgBox "One record written to Sheet1"

          response = MsgBox("Do you want to enter another record?", _
              vbYesNo)

          If response = vbYes Then
            DH.Value = ""
            DHNum.Value = ""
            DHCst.Value = ""
            Rsn.Value = ""
            VnNum.Value = ""
            VnCst.Value = ""
            VnAd.Value = ""
            VnPh.Value = ""
            VnWb.Value = ""
            VnCt.Value = ""
            Vn.Value = ""
            VnZip.Value = ""
            st.Value = ""
            VnRsn.Value = ""
            Req.Value = ""
            ReqD.Value = ""
            TT.Value = ""
            TTNum.Value = ""
            TT.SetFocus
          Else
            Unload Me
          End If

End Sub