Doubt declare SQLServer

I'd like to know, if there is a possibility reference declare SQLServer dynamically?

For example, I've tried execute this query(under), but I received this message (Server: Msg 137, Level 15, State 1, Line 6
Must declare the variable '@t1'.):

declare @Frase varchar(50)
set @Frase = 'declare @t1 varchar(10), @t2 int'
exec (@Frase)
select @t1 = 'AAAAA'
select @t2 = 1000
Print @t1
Print @t2

I need to do this because 1) I get informations about specific table (sysobjects and syscolumns); 2) In relation to these columns I'll create a declare to use with a cursor, but unfortunately I can't.

Thanks.

why don't you just declare the variables instead of trying to exec a statement?