Access Cookbook - Ken Getz [198]
' the user cancelled, so preserve the existing value.
If Not IsNull(varReturn) Then
ctlDate = varReturn
End If
End Sub
Change txtApptDate to the name of the text box created in this step.
Save the form, switch to form view, and test out the new pop-up form by clicking on the cmdPopupCal button.
Discussion
You insert a custom control into an Access form using the Insert → Custom Control command. The control can then be moved and resized as necessary. When you insert a custom control into an Access form, Access merges the properties of the control's container (a bound or unbound OLE frame control) with the properties of the custom control. The custom control's unique properties are placed on the Other tab of the control's regular properties sheet, but you can also manipulate these properties using the custom properties sheet created by the control's creator. You do this by right-clicking on the control and selecting Calendar Control Object → Properties from the shortcut menu.
ACCESS AND CUSTOM CONTROL DATA BINDING
Access supports simple custom control data binding. This means you can use controls (such as the Calendar control) that are bound to a single field, but you can't use certain types of bound controls (such as Visual Basic's Data-Bound Grid control) that are bound to tables or queries. You can, however, use controls such as Data-Bound Grid control in Access if they are used in unbound mode.
In Step 3 of adding a bound Calendar control, you bound the Calendar control directly to a field in the form's underlying record source.
In the steps for creating a generic unbound pop-up calendar form, you created code that manipulated five different methods of the Calendar control: PreviousYear, NextYear, PreviousMonth, NextMonth, and Today. For example, in the event procedure attached to cmdPreviousMonth, you added the following line of code:
Me.ocxCal.PreviousMonth
TIP
To find additional information on the methods, properties, and events of a particular custom control, you can use the Help button that appears on some (but not all) controls' custom properties sheets (see Figure 9-31). Alternately, you may have to load the control's help file separately or consult its printed documentation or electronic README file.
The frmPopupCal form contains two special procedures, called property procedures, that you may not have seen before. Using property procedures, you can create custom properties for a form that can be called from outside the form. This allows you to expose certain elements of the form to the outer world while keeping all of the form's controls and procedures—the form's inner workings—encapsulated within the form.
The Let property procedure creates a user-defined property for the form, controlling what happens when a calling routine sets the value of the form's property. The Get property procedure controls what happens when a calling routine requests the value of the property. The property procedure for frmPopupCal is simple, consisting of only an assignment statement, but you can do anything in a property procedure that you could do in a normal event procedure. For example, you can count the number of text box controls on a form in a Get property procedure, or you can set all the labels on a form to a certain color in a Let property procedure. The Solution in Recipe 9.10 contains examples of more complex property procedures.
TIP
The data type of the parameter of the Let procedure (or of the last parameter, if the Let procedure contains multiple parameters) must match the data type of the return value of the Get property procedure.
The basCalendar module contains a wrapper function for the frmPopupCal pop-up calendar form. The acbGetDate wrapper function is shown here:
Function acbGetDate(varDate As Variant) As Variant
Const acbcCalForm = "frmPopupCal"
' Open calendar form in dialog mode, passing it the current
' date using OpenArgs.
DoCmd.OpenForm acbcCalForm, WindowMode:=acDialog, OpenArgs:=Nz(varDate)
' Check if the form