Weird Proc Syntax Error

'Ello there. This proc has been giving me headaches for a week now, hopefully someone here knows whats wrong with it.


CREATE PROC [dbo].[search_querry_results](
@datefrom datetime = NULL,
@datetodatetime = NULL,
@querry_string varchar(60),
@slice int
)
AS

DECLARE @querry nvarchar(2000)
SET @querry = 'SELECT TOP ' + CAST(@slice AS varchar(100)) + ' * FROM FREETEXTTABLE( Exponent, *, ''' + @querry_string + ''' ) as ct JOIN Exponent AS e ON ct.[KEY] = e.[Key] WHERE date > ' + CAST( @datefrom AS varchar(30)) + ' AND date < ' + CAST(@dateto AS varchar(30)) + ' ORDER BY Rank DESC'

BEGIN
IF ( @datefrom IS NOT NULL ) AND ( @dateto IS NOT NULL )
EXEC sp_executesql @querry
END
GO


I am running it from Query Analyzer using the following line

EXEC search_querry_results @datefrom = '01/01/1970' , @dateto = '01/01/1980', @querry_string = 'Student' , @slice = '10'


The error it is giving me is: Line 1: Incorrect syntax near '1'.

Anyone have any ideas what is going wrong?