I'm not 100% sure what you are asking for in Question 1 (it almost sounds like you want an Outlook macro rather than an Excel macro)... can you give us a more detailed description of what you want here? As for Question 2, I think this code will do what you want (just change the Path and BaseName variable assignments to what you actually are working with)...
Dim Path As String, BaseName As String, FileName As String, LatestFile As String
Path = "c:\Temp\Test" '<== Notice the trailing backslash
BaseName = "xxxx"
FileName = Dir(Path & BaseName & "*.xlsb")
Do While Len(FileName)
LatestFile = Path & FileName
FileName = Dir()
Loop
MsgBox "Latest file name and path is.... " & LatestFile