MS Access 2019: How do I check for duplicate records before update, then run a specific procedure if duplicates are found? - vba

Question

I am very new to both StackOverflow and to doing any sort of advanced programming in MS Access. I created a database to catalog my trading card collection (Excel just wasn't cutting it since we're talking about over 2000 unique cards). At first it was just a simple table of records, but now it's turned into a full-fledged database that I have search forms for and queries and everything.
What I'm trying to do right now is streamline my process a bit, and there is something very specific that I want to make Access do. I'm almost certain that whatever I want to do will have to be done in VBA, and I'm just not familiar enough with it to do what I want.
What I want it to do is this: Any time a new record is entered, I want it to check the record before it saves the record into the DB (I'm fairly confident that I need to use the "Before Update" event for this) and make sure that the "Sort ID" field (an auto-calculated field I've created) contains no duplicates (I know I'll most likely have to use queries for this since auto-calculated fields can't be indexed). If the program detects a duplicate, I want it to produce a message box saying that I'm trying to enter a duplicate record and ask me if I want to update the "number owned" field of the existing record instead of creating a new one, and then take me to the record in question on an affirmative response.
What I currently have is a validation rule that uses an index (comprised of the fields that generate the Sort ID), which generates a custom error message by using the following VBA code in the "On Error" event:
Private Sub Form_Error(DataErr As Integer, Response As Integer)
Const conErrRequiredData = 3022
If DataErr = conErrRequiredData Then
MsgBox ("Duplicate Sort ID. Please update the 'number owned' field on the existing record instead.")
Response = acDataErrContinue
Else
Response = acDataErrDisplay
End If
End Sub
This code works exactly as it should, but I want more than a pop-up error that I can't do anything with. I have a query entitled "CheckDuplicateSortID" that I created using the Query Wizard, and it checks the "Sort ID" field for duplicates, but that's as far as I've managed to get. The example on This site is about the closest I've managed to find to what I'm looking for, but the code sample given is very difficult for me to understand because there's very little explanation with it; I'm not familiar enough with Access VBA to know which parts are important code and which parts are his specific field names and other variables; I haven't gotten any error messages because I'm stumped on even trying to figure out what needs to be changed from that sample code and what it needs to be changed to.
Edit: Just for the sake of clarification, the solution doesn't have to involve the Sort ID field. I created that so I'd have one field I can point the program to. But if it would be simpler to just use the index that I use for my current validation rules (with the error message generated by the above code), I'm open to that too.

Answer 1

After some considerable finagling, I actually managed to find a solution to this on my own, though it is probably needlessly complicated (I'm definitely open to simpler solutions, if anyone has any).
Rather than using the actual SortID field, I modified the code in the OP to this:
Private Sub Form_Error(DataErr As Integer, Response As Integer)
Dim strMsg As String
Dim iResponse As Integer
'The text to be displayed in the message prompt.
strMsg = "Unable to save record. The values you have entered would generate a duplicate." & Chr(10)
strMsg = strMsg & "Would you like to clear this form and edit the existing record instead?"
'Calls for the yes/no message prompt specifically when the no-duplicate
'validation rule is violated (error 3022).
Const conErrRequiredData = 3022
If DataErr = conErrRequiredData Then
iResponse = MsgBox(strMsg, vbQuestion + vbYesNo, "Invalid Sort ID")
Response = iResponse
If iResponse = vbYes Then
'Calls a custom function that opens the record in question for editing.
UpdateOnError
Else
'Cancels the operation on a negative response and does not clear the form.
Cancel = True
End If
Else
Response = acDataErrDisplay
End If
End Sub
As you can see from the above code, the event calls a custom function, which is coded as follows:
Function UpdateOnError()
On Error GoTo UpdateOnError_Err
Dim UpdateGoToID As Variant
'Selects the Sort ID in question for the purpose of opening the existing record.
UpdateGoToID = Forms![Card List Entry Form]!txtSortID
'Clears the invalid form.
DoCmd.RunCommand acCmdUndo
'Opens the existing record the user attempted to duplicate.
DoCmd.OpenForm "Card List Entry Form", acNormal, "", "[Sort ID]=" & "'" & UpdateGoToID & "'", , acNormal
UpdateOnError_Exit:
Exit Function
UpdateOnError_Err:
MsgBox Error$
Resume UpdateOnError_Exit
End Function
Like I said, this is probably a lot more steps than actually needed, but it does work as I want it to: when the user attempts to enter a duplicate record, an error message pops up asking if they would like to update the existing record. If yes, it takes them to the existing record. If no, it closes the error message without clearing the form or saving the record.