Concatination Help Required From Gurus!!

I need to execute the following code by passing the username as a parameter.Can I get help to complete the SQL statement??

exec ('sp_changeobjectowner '+ @Table_name +','+@ToUser) ---> This works fine.

But I need to have something like this:

exec ('sp_changeobjectowner '@username.+ @Table_name +','+@ToUser)

Note:
Here is the sample working syntax:
sp_changeobjectowner 'user1.eb_sku', user2

So,I need user1 and user2 as two different parameters.

As you see,I need to qualify the table name with the owner name which itself I want to pass as a parameter.

Any help with syntax is greatly appreciated!!
Di.