HTML field accepts only the numbers of a Query (SQL-Server)

I have the following field:

Código da Receita: 
<input type="text" name="cod_receita"> 

and would like it to accept only the numbers for this query:

SELECT distinct orcplare.codigo 
 FROM rectotor 
 INNER JOIN orcplare ON 
        (orcplare.codigo = rectotor.codigo_receita) 
WHERE   rectotor.data_movto between '1-1-1996' and '31-12-1996'
ORDER BY codigo 

What would be the best way for me to do this?