how to pass selected item from listbox of one form to text box of other form in javascript and html

i call given given below function setpara() in onchange event of listbox control

function setpara()
//alert('Hey I said not to try clicking this link');



here t1 and t2 are textbox names

and cns_1 and cns_2 are listbox names

and f1 and form11 are form names

but stilll this code is not work
what to