See CREATE FUNCTION in BOL

>How to do that?
>
>>Make it into table-valued UDF.
>>
>>>
>>>I have a view that calculates the Stock Balance upto current date. It is working for me.
>>>
>>>

>>>SELECT     tmp.mcat_code, tmp.mat_code, Mat.mcat_desc, Mat.mat_desc, SUM(tmp.qty) AS qty
>>>FROM         (SELECT     mcat_code, mat_code, SUM(qty) AS qty
>>>                       FROM          mat_ob
>>>                       GROUP BY mcat_code, mat_code
>>>                       UNION
>>>                       SELECT     mcat_code, mat_code, SUM(qty) AS qty
>>>                       FROM         Purchase
>>>                       GROUP BY mcat_code, mat_code
>>>                       UNION
>>>                       SELECT     mcat_code, mat_code, SUM((con_qty + wst_qty) * - 1) AS qty
>>>                       FROM         Production
>>>                       GROUP BY mcat_code, mat_code ) AS tmp INNER JOIN
>>>                      Mat ON Mat.mcat_code + Mat.mat_code = tmp.mcat_code + tmp.mat_code
>>>GROUP BY tmp.mcat_code, tmp.mat_code, Mat.mcat_desc, Mat.mat_desc
>>>ORDER BY tmp.mcat_code, Mat.mat_desc
>>>

>>>
>>>What i do if I want stock balance for certain date. Parameterized view? how to create it?
>>>
>>>Zahid