MySql访问VB

Question

My application is
Microsoft Access front end
MySql back end
Code is in vb

I am trying to modify a form that has a few drop down fields [![enter image description here][1]][1]. I need it to require the jobcustomerID before updating. Right now if i add an address first it will tell me to add the customer but gives me an error for "invalid use of null"

Current Code

    Private Sub Form_BeforeUpdate(Cancel As Integer)
       If IsNull(Me.JobCustomerID) Or Me.JobCustomerID = "" Then
            Call MsgBox("You must select a Customer from the list provided", vbExclamation, "REQUIRED ENTRY")
             Me.JobCustomerID.SetFocus
             Cancel = True
             Exit Sub
           End If
       End Sub

I do have an image of the fields but lack the reputation needed

Answer 1

Try moving the cancellation to the front.

If IsNull(Me.JobCustomerID) Or Me.JobCustomerID = "" Then
    Cancel = True
    MsgBox "You must select a Customer from the list provided", vbExclamation, "REQUIRED ENTRY"
    Me.JobCustomerID.SetFocus
    Exit Sub
End If