Parameters And Table Names

Please help,
I am inserting data into a newly created table with many rows similar to thoes below using a sp with a parameter @Extract
CREATE PROCEDURE mytest
@Extract int
AS
DECLARE @MyName varchar(25)--these keep changing for each total
DECLARE @Counter varchar(2)--this will increment from 2 to 40
SELECT @MyName ='tblG3>74Ex' +convert(varchar(3), @Extract)
SET @total1 =(SELECT COUNT(*)
FROM @MyName
WHERE (sSurgery_id ="S0" + @Counter) and (iExtract_nm = @Extract)
SELECT @MyName ='tblG335-74Ex' +convert(varchar(3), @Extract)
SET @total2 = (SELECT COUNT(*)
FROM @MyName
WHERE (sSurgery_id ="S0" + @Counter)and (iExtract_nm =@Extract)
insert into tblNew([35-74],[>74],etc,etc,Report4)
values (@total1,@total2,ect,ect,@report4)
it all works until I try to use the @MyName
Please put me out of my misery
Many thanks
David