Execute a sentence into a procedure (SQL Server)

I have declared a varchar variable, and it contains a sql sentence (which it works), I want to execute this sentece into a procedure.
If I use:
EXECUTE @sentence;

I get this error: "insert into..... (all sentence)" isn't a valid identifier.

How can I do that?
Thank you in advance.

maybe you need to use ( )
something like this :

Code:

---

declare @sentence varchar(100)
set @sentence='select * from employees'
exec (@sentence)

---

which works fine.