Implementing the Calandar, Page 4

By itself the Calandar application only has a limited use as a stand alone application. To get the most use from the application it needed to built in such a fashion so that it could be used not only as a stand alone application but also as a reusable component that could be re-used in other applications.

As described above the calendar application is ready to go as a stand alone application which will accept a command line argument of any valid date but to be useful with other Windows applications it will need the ability to pass the users selected date back to the calling application. There are already a number of VBX Calendar applications commercially available but these were designed and implemented before the release of Win95 and all unfortunately do not reflect changes made to the International settings in Win95. At first sight it would therefore seem logical to take the prototype calendar application developed in Visual Basic and to rewrite it as an OXC implementation that could be used as an add-on component for any VB application that required calendar functionality. However as I almost exclusively use VB and as I did not wish to go to the trouble of having yet another VBX/OCX file to remember to distribute with my applications I did not persue the development of a Calendar OCX. Also the code that I have used works equally as well(except for international considerations) with the 16 and 32 bit versions of VB as well as with Access. Instead I have chosen to use the application as is and to store the form file as a read-only file that I could then include in my applications or copy and paste from the file to implement different versions of the same calendar application ( see CALENDAR.FRM included in CALENDAR.ZIP which can be downloaded from this ftp site).

To add calendar functionality to any exiting VB project simply add the calendar.frm to your VB project and add a button which the user can click in order to display the form and select a date. eg.

  Private Sub cmdGetDate_Click(Index As Integer)
    Select Case Index
      Case 0
        SettlementDate = GetDate_Dialog(SettlementDate)
      Case 1
        MaturityDate = GetDate_Dialog(MaturityDate)
      Case Else
    End Select
  End Sub

  Function GetDate_Dialog(Optional dt As Variant) As Variant

  ' Show and display the Calendar dialog and return the chosen date.
      Load Calendar
    If IsDate(dt) Then
      Calendar.lblLastDate = dt		          ' tell the Calendar form to display the
  passed date
    Else
      Calendar.lblLastDate = Date		  ' default to todays date if no date passed
    End If
    Calendar.Show 1
    GetDate_Dialog = Calendar.DateSelected	  ' get the users selected date
    Unload Calendar
    Set Calendar = Nothing			  ' free memory resources
  End Function

The most common use of a calendar application however is not as free floating form but rather as a component on a form in some other application like an appointment book. To implement calendar functionality simply copy and pasted the controls and code from the Calendar form into a containing form. I have stored the calendar application in a library using my product Object Library from which I can simply drag and drop the complete calendar (controls and code) directly into a containing form. As the calendar is made from lightweight controls there are no overheads involved in adding additional OCX or VBX files to my project to implement calendar functionality.

The beauty of this VB application is that all of the code used in the VB form can be reused in equivalent applications for MS Access, MS Excel and MS Word with little or no modification to the syntax. An access equivalent calendar is included with the ZIP file that accompanies this article.

A listing of VBA date functions and subroutines.

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