Get the last date(last day) of the month with Excel VBA DateSerial

Hello,

With the following code I get the first date(first day) of the last month, in this case it is "02-01-2015":

 Format(DateSerial(Year(Date), Month(Date) - 1, 1), "mm-dd-yyyy")

Now, how can I get the last date(last day) of the last month using the same portion of code above? I should get "02-28-2015"

Thanks!