Pop-up, Modal, or Dialog FormsAccess forms can be opened within your application in three different window modes: Popup, Modal, or Dialog. These can be set manually using the property sheet or programmatically using VBA or macros. Each mode behaves differently and can be used for different purposes. You can also combine the modes to have even greater control over the way the user can interact with the form and the entire application when the form is open.
Pop-upA pop-up form opens and stays on top of all other open forms within your application (actually, the pop-up form opens outside of the Access application window). Although it is on top of other objects, the pop-up form does not necessarily have to have the focus. This can be quite helpful when you want to present the user with some reference information that needs to be available while they are using or entering data on another form. A pop-up form also allows the user to access the ribbon buttons and menus.
You can create a pop-up form by setting its PopUp property to Yes. This property is often used in conjunction with setting other properties such as Modal, Cycle (of records) and Border Style.
ModalA modal form opens and keeps the focus until it is closed (or hidden). When a modal form opens, the user will not be able to use other forms or even go to the ribbon (it won’t even let you click the Exit button to quit Access). This mode is useful when you want to control the user’s workflow by opening each modal form in sequence based on the task they’re doing.
You can create a modal form by setting the form’s Modal property to Yes. If you use both the PopUp and Modal properties, you can make the form behave both as a pop-up (stays on top) and a modal (keeps the focus) form by setting them both to Yes.
DialogA dialog form opens on top of all the other forms and also keeps the focus until it is closed (or hidden). There is one major difference with a dialog form’s behavior as compared to a form with its PopUp and Modal properties set to Yes. When a form is opened in dialog mode, all code execution is also “suspended” until the dialog form is closed. This type of behavior is very useful when you need user input before proceeding with the next logic in your code. Some examples of dialog forms are the “warning” messages from Access or the MsgBox() and InputBox() functions.
You can only open a form in dialog mode using code (VBA or macro). The form can be opened in dialog mode regardless of the PopUp and Modal property settings. You can use either of the following lines of code to open a form in dialog mode,
DoCmd.OpenForm "FormName", , , , , acDialog
DoCmd.OpenForm "FormName", WindowMode:=acDialog
(The above excerpt can be found in Chapter 17, Page 262 of the book "Professional Access 2013 Programming.")
Original post date: October 2, 2013