Yes/No Calculated Column for Last Month

I have the following code to create a calculated column returning "Yes" if the selected date was last month and "No" for everything else.  This was working fine until this month due to the year change.  I know what the problem is, but I'm not sure how to correct it.

Here is the custom column code;

if (Date.Year([RequestReceived]) = Date.Year(DateTime.LocalNow()) and Date.Month([RequestReceived]) = Date.Month(DateTime.LocalNow())-1) then "Yes" else "No"

It's clear that the problem is that the code is looking to see if the year matches then looking to see if the month is the current month minus one.  This was needed so the formula was taking into account both year and month.  Of course, last month's year will not match, so I'm not getting the correct result from the formula.  I expect that in February this code will work fine again, but every January it will not.  How can I revise this, or better calculate if the date in the selected field was last month?

Thanks,

Shawn