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Decision making in VBA

Decision making in VBA. Current Event. Occurs: When a form is opened When the focus leaves one record and moves to another Before the first or next record is displayed. Disable next record button. Private Sub Form_Current() If Me.NewRecord = True Then cmdPrevRec.SetFocus

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Decision making in VBA

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  1. Decision making in VBA

  2. Current Event Occurs: • When a form is opened • When the focus leaves one record and moves to another • Before the first or next record is displayed

  3. Disable next record button Private Sub Form_Current() If Me.NewRecord = True Then cmdPrevRec.SetFocus cmdNextRec.Enabled = False End If End Sub

  4. Re-enable next record button Private Sub Form_Current() If Me.NewRecord = True Then cmdPrevRec.SetFocus cmdNextRec.Enabled = False Else cmdNextRec.Enabled = True End If End Sub

  5. Disable previous record button Private Sub Form_Current() If Me.NewRecord = True Then cmdPrevRec.Enabled = True cmdPrevRec.SetFocus cmdNextRec.Enabled = False ElseIf Me.CurrentRecord = 1 Then cmdNextRec.Enabled = True cmdNextRec.SetFocus cmdPrevRec.Enabled = False Else cmdNextRec.Enabled = True cmdPrevRec.Enabled = True End If End Sub

  6. Trappable errors • Can occur while application is running • Each has a unique error number • Type “Trappable errors” in VBA help to get complete listing • When these errors occur for a form (or report) we can use the objects Error event to respond to them.

  7. Display error number Private Sub Form_Error(DataErr As Integer, Response As Integer) MsgBox DataErr End Sub

  8. Code to handle trappable errors Private Sub Form_Error(DataErr As Integer, Response As Integer) Select Case DataErr Case 2237 MsgBox "You have entered a title that is not in the list.” _ “ & “Click the list and choose one of the options shown." Response = acDataErrContinue Case 3314 MsgBox "You must enter both first and last name for the employee.” _ & “Fill in the missing value." Response = acDataErrContinue Case 3317 MsgBox "Employee start date must be today's date or earlier.” _ & “Please enter a valid date" Response = acDataErrContinue Case Else'the default error handler displays VBA error message Response = acDataErrDisplay End Select End Sub

  9. Control Wizard error-handling Private Sub cmdNextRec_Click() On Error GoTo Err_cmdNextRec_Click DoCmd.GoToRecord , , acNext Exit_cmdNextRec_Click: Exit Sub Err_cmdNextRec_Click: MsgBox Err.Description Resume Exit_cmdNextRec_Click End Sub

  10. Function without error handling Public Sub TestErrors() Dim dblResult As Double dblResult = 10 / InputBox("Enter a number") MsgBox "The result is " & dblResult End Sub

  11. Error handling added Public Sub TestErrors2() On Error GoTo Err_TestErrors Dim dblResult As Double dblResult = 10 / InputBox("Enter a number") MsgBox "The result is " & dblResult Exit_TestErrors: Exit Sub Err_TestErrors: Select Case Err.Number Case 11 'division by zero dblResult = 0 Resume Next Case 13 'type mismatch Resume Case Else MsgBox Err.Number & ": " & Err.Description Resume Exit_TestErrors End Select End Sub

  12. Select Case statement Syntax Select Casetestexpression[Caseexpressionlist-n[statements-n]] ...[Case Else[elsestatements]] End Select

  13. Select Case Example Public Function Discount(curAmount As Currency) Select Case curAmount Case Is >= 100 MsgBox "10% discount" Case Is >= 50 MsgBox "5% discount" Case Else MsgBox "No discount" End Select End Function

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