Make a button have multiple uses - vb.net

Question

okay... How do I explain this without being totally confusing?... Alright, I have this form that has MenuScripts (top-levels and second-levels). The problem that I am having is one of the second-levels is "Add" which brings you to another form when clicked. This other form has a button ("Record") and text boxes. This other form allows the user to input data and when the record button is clicked, the inputted data is written into a text file. Ok, so back to the first form. Another second-level MenuScript is "Update" which also brings the user to the other form; but first, the user has to click an item within a listbox to proceed. How do I get the data from the selected item to appear in the appropriate textboxes and how do I get the record button to update data instead of being confused and thinking it is only a add-data button?
Is there a way to use an "if" statement to say something like "if mnuAdd is clicked then" "elseif mnuUpdate is clicked then". Would something like that work for giving the record button multiple uses?
Also, if someone can give me some pointers on making sure the user selects an item within the listbox would definitely be a plus! Thanks, guys!
Unfortunately, I cannot add images since my reputation is too low.
Here is a visual representation of my ultimate goal

Answer 1

Easiest way: before displaying the second form set it's Tag property to something distinct – say "Add" or "Update" – depending on which menu item is selected. Then you just test the Tag value in the button's Click event and proceed accordingly.
As for determining whether a list item is selected: well if there isn't the ListBox's SelectedIndex property will be set to -1.

Answer 2

You need to put a public property on the second form (Details) which specifies which mode it is in. For instance, you could create a mode enumeration like this:
Public Enum EntryModes
AddBook
UpdateBook
End Enum
Then, define a public mode property on the second form, like this:
Public Property EntryMode As EntryModes
Get
Return _entryMode
End Get
Set(ByVal value As EntryMode)
_entryMode = value
End Set
End Property
Private _entryMode As EntryMode
Then, when you show the second form from the menu, just set the property first, before showing it:
Private Sub mnuAdd_Click(sender As Object, e As EventArgs)
Dim dialog As New DetailsDialog()
dialog.EntryMode = EntryModes.AddBook
dialog.ShowDialog()
End Sub
Private Sub mnuUpdate_Click(sender As Object, e As EventArgs)
Dim dialog As New DetailsDialog()
dialog.EntryMode = EntryModes.UpdateBook
dialog.BookToUpdate = ListBox1.SelectedItem
dialog.ShowDialog()
End Sub
As you can see, in the Upate menu click, I also added a line that passes the information for which book should be updated.