Passing parameter in URL to the Parameter textBox of SSRS

Hi.

I have this url:

http://sql01/Reports_MSSQLSERVER_YSE/Pages/Report.aspx?ItemPath=%2fGestaoFormacao%2fAccoes%2finquerito_3M_colaborador_v2&rs:Command=Render&Accao=21

But when i open the report the textbox with the parameter Accao is empty.

I have tried various solutions, but nothing. The parameter TextBox is empty all the time.

Any idea?

What am i doing wrong?

Thank's in advance