You are nearly there, but you need to check the return of dlgSaveAs.Show, that wil be -1 (a filename selected) or 0 (cancel).
Then get the filename from dlgSaveAs.SelectedItems(1)
Dim dlgSaveAs As FileDialog
Dim strMyFile As String
Set dlgSaveAs = Application.FileDialog(fileDialogType:=msoFileDialogSaveAs)
.InitialFileName = "Presentation2_" & Format(Date, "yyyy-mm-dd")
If .Show = -1 Then
strMyFile = .SelectedItems(1)
'-- save your file to strMyFile here
'-- The user pressed Cancel.
Set dlgSaveAs = Nothing