Questions about php

Hi.... i have a trouble with php. i hope not not be on a off-topic situation... if yes please sorry. i´am trying to make a php page which has to make the following things: it´s a page for making computers configurations for the public, so: it has combo boxes fro the selection of the component, for example the customer selects a processor from the combo and then the price of the selected processor has to appear in a text box near it..... that´s the problem i have....... every thing works ok.. i fill the combo but when i choose an processor from the list the event 'onchange' should have been trigged.. well...... this is the function i have from the event.... function precio ($control) { if($control == 'cmb_procesadores') precio_procesador.value = '12200'; }; and thats is the line of the object and the what to do on event onchange echo("Procesadores : <select name=\"cmb_procesadores\" onchange=\"precio(cmb_procesadores)\" >"); and nothing happends when i click cmb_procesadores.... what am i doing wrong???.... any help.. please....... also.... i have a text box... echo("<input type=\"text\" name=\"precio_procesador\">"); how do i reference the object for setting its value to the price of the processor returned of a sql sentence????????? in general how do i reference a propietie of an object??? from example as precio_procesador.value.... or something like this...... thanks in advance... Julio Saura Alejandre Departamento de I+D Grupo InterApp