Using a calculated field for a restriction in SmartList Builder (get records from last month)

I want to use add a date restriction to the SmartList to show Last Month's transactions since most of the time people are looking at last month's transactions when closing a month, etc.  One of the things I noticed on date restrictions built into SmartList is that it only has first day of current month and last day or current month, but they don't have last month.

I created a calculated field like this that calculates the first day of last month and the last day of last month (TSQL functions):

FirstDayofLastMonth

DATEADD(MONTH, DATEDIFF(MONTH, 0, GETDATE()) - 1, 0)

LastDayOfLastMonth

DATEADD(DAY, -(DAY(GETDATE())), GETDATE())

However, when I use a restriction on the SmartList, and I select the Document Date field from the RM Open File, I don't see a way for me to select the calculated field.  

Does anyone know how to do this without creating SQL views?   Our client doesn't have access to their back end, so we can't really do that without some major red tape.

Thanks for the help in advance!