GRANT EXECUTE ON SP BY USER

use [YOUR DATABASE]
GO

/*
SELECT * FROM sys.objects
where [type] = 'p' and is_ms_shipped = 0 and name not like 'sp_%'
order by name
*/

DECLARE @proc VARCHAR(255)
DECLARE @user VARCHAR(255)
DECLARE @cmd NVARCHAR(500)

SET @user = '[NT AUTHORITY\NETWORK SERVICE]'

DECLARE ProceduresCursor CURSOR FOR
    SELECT name FROM sys.objects
    WHERE [type] = 'p' and is_ms_shipped = 0    and name not like 'sp_%'
    ORDER BY name

OPEN ProceduresCursor
FETCH NEXT FROM ProceduresCursor INTO @proc
WHILE @@FETCH_STATUS = 0
BEGIN
    SET @cmd = 'GRANT EXECUTE ON [dbo].[' + @proc + '] TO ' + @user
    EXEC (@cmd)
    --PRINT @cmd
    FETCH NEXT FROM ProceduresCursor INTO @proc
END
CLOSE ProceduresCursor
DEALLOCATE ProceduresCursor