Combining columns in WHERE IN clause

I get an error when trying to process this SQL statement.  What is the proper way to concatenate the names of two columns in the WHERE and SELECT clauses?

SQL = SELECT * FROM @SearchTbl WHERE Name + Date As NameDate IN (SELECT Name + Date as NameDate FROM @SearchTbl WHERE thatNum = X and thisNum = 12)

Thank you,

Gina

Gina