Problem In Cursor

[shakti5385]

Hi all
I am facing some problem in cursor.

ALTER PROCEDURE [dbo].[Product_Despatch_Return]
@Search_Transaction_ID int,
@Search_Product_Name nvarchar(50)
AS
BEGIN
	SET NOCOUNT ON;
	DECLARE 	@QueryString nvarchar(MAX)

SET @QueryString='SELECT Product_Transction.Transaction_ID AS Transaction_ID, Product_Transction.Transaction_Date AS Transaction_Date,Product_Transaction_Details.Product_Id AS Product_Id, Product_Master.Product_Name AS Product_Name,Product_Transaction_Details.Qty AS OrderQuantity,Product_Transaction_Details.Details_Id AS Product_Transaction_Details_Id FROM Product_Transction INNER JOIN  Product_Transaction_Details ON Product_Transction.Transaction_ID = Product_Transaction_Details.Transaction_Id INNER JOIN  Product_Master ON Product_Transaction_Details.Product_Id = Product_Master.Product_ID WHERE Product_Transction.Is_Deleted=0 AND Product_Transaction_Details.Is_Deleted=0 '
	-- CHECKING THE @Search_Transaction_ID
	IF NOT (@Search_Transaction_ID=NULL OR @Search_Transaction_ID=0)
	BEGIN
		SET @QueryString=@QueryString+ ' Product_Transction.Transaction_ID='+CAST(@Search_Transaction_ID AS NVARCHAR)
	END
	-- CHECKING THE @Search_Product_Name
	IF NOT (@Search_Product_Name=NULL OR @Search_Product_Name='')
	BEGIN
		SET @QueryString=@QueryString+ ' Product_Master.Product_Name='''+@Search_Product_Name+''''
	END

	DECLARE C CURSOR FOR @QueryString ' Error is Here
	OPEN C

I am facing error in the next line.
DECLARE C CURSOR FOR @QueryString ' Error is Here
Incorrect syntax near '@QueryString