Help with SQL SELECT, .idc

I am currently working on updating a web page that uses .idc files. The site is an auction house and the catalogue is stored on a database that uses .idc and .htx files to show it to users. Each catagory has a different prefix, ie.
B1 = Books, lot 1
F3 = Furniture, lot 3
etc...
At the moment when you want to view the catalogue, the entire catalogue is shown but I want to make it so when you are on the Books topic page, only the books catalogue is displayed and when you are in the Furniture topics page, only the furniture lots are displayed, and so on through all the departments. The current .IDC code looks like this...
Datasource: auction
Template: lotdetails.htx
SQLStatement: SELECT sale, REPLICATE("0",8-LEN(ALLTRIM(lotno)))+lotno AS lotnox,lotno,low_est,high_est,description, pict_name, price, itemkey, ALLTRIM(SUBSTR(ALLTRIM(pict_name),1,LEN(ALLTRIM(pi ct_name))-4)) AS pictname
+FROM lothedrs
+WHERE lothedrs.sale = "%sale_key%"
+AND REPLICATE("0",8-LEN(ALLTRIM(lotno)))+lotno =>
+ REPLICATE("0",8-LEN(ALLTRIM("%lotstart%")))+"%lotstart%"
+ORDER BY lotnox
DefaultParameters: lotstart = 0
MaxRecords: 25

I don't know what extra code I need to instruct the program to only display lot numbers with a certain prefix. If anyone can help I would be greatly appreciative.

Pete