How To Create Store Procedure To Use With Dropdownlist

Dear all,

i want to create a storeprocedure that may acept value such as  0,1, 1a, 2, 2a etc.. from a dropDownList. But i always get an error. below is sample of my SQL1 DECLARE @val varchar(5)
2 DECLARE @sql varchar(4000)
3
4 SET @val = '1a'
5 SET @sql = 'select * FROM [dbo].[vwFormNAllAnswers]'
6
7 IF @val NOT LIKE '0'
8 SET @sql = @sql + 'WHERE QuestionCode LIKE '+ @val
9
10 EXEC(@sql)