How To Use Variable In SELECT DISTINCT

Is it possible to use a variable in the first line of the following code?

Code:
SELECT DISTINCT [June-11].[Full Name], [June-11].[Level 8 Name]
FROM [June-11]
WHERE ((([June-11].[Level 6 Name])="SMITH, BOB") AND ((Exists (SELECT * FROM [July-11]
WHERE [June-11].[Full Name] = [July-11].[Full Name]))=False));

I have a combo box that lists months and I want to be able to choose which month goes in the SELECT DISTINCT line of code. So, where it says [June-11], I would like it to reference my combo box so I can select the month.