It does depend on how you defined "used". You could also take a look at the index usage statistics to see how often a clustered index (which is a table) or a heap (table w/o a clustered index) is accessed. This is a really simple example:

SELECTOBJECT_NAME(object_id, database_id) AS ObjectName,

ddius.user_lookups,

ddius.user_scans,

ddius.user_seeks,

ddius.user_updates

FROMsys.dm_db_index_usage_stats AS ddius

WHEREOBJECTPROPERTY(ddius.object_id, 'IsUserTable') = 1;