Replace Error 3022 VBA with specific field labels

Hello!

tblEmployee with EmployeeIDpk and LName (holds employee data)
tblEvent with EventIDpk and Event (holds event data) (Check-in,
orientation, CPR training, etc.)
tblEmpEvent with EmployeeIDfk and EventWhenIDfk (holds which
employees did which events)
tblEventWhen with EventWhenIDpk, EventIDfk, EventDate (holds when each
event happened)

I use a mainform based on tblEventWhen where I enter the date and then
select the event via a combobox tied to tblEvent.
On that mainform is a continouus subform where I select which
employees did that event

Some rules:
1) An event cannot happen more than once a day. (EventDate and Event
are the same)
2) An employee cannot do the same event more than once. (Event and
EmployeeIDpk are the same)

For #1, I use the following:

Private Sub Form_Error(DataErr As Integer, Response As Integer)
If DataErr = 3022 Then
MsgBox "This combination of date and event has already been entered. "
& "Please use the previous entry to prevent duplication of data.",
vbExclamation, "Duplicate Date-Event Combination"
Response = acDataErrContinue
End If
End Sub


I am stumped about #2 and would like to do away with the whole Error
3022 route for #1, and go with some VBA like:

If the combination of EventDate and Event, or the combination of Event
and EmployeeIDfk, contain duplicates, display a messagebox stating
"[LName] previously completed the [Event] event on [EventDate]. Please
update or delete the previous entry, then reenter the new event data."

(I set up two duplicate records queries and that works, but it catches
duplicates after entry instead of as they are being entered.)

??

VR/Lost