CRM 2011 Opportunity entity

Hello-

I created the following script in CRM 2011 to change the required level of a field.  It is not working.  Can anyone assisst me with why thi sis not working?  What am I missing?

function Form_OnSave() {  

}  

function Form_OnLoad() {

function setrequire()

}

function setrequire()

var type = Xrm.Page.getAttribute("cprs_type").getSelectedOption().text;

if (type == "Option5")    

{

then Xrm.Page.getAttribute("cpdc_primarypracticearea").setRequiredLevel("none");

}

else

{

Xrm.Page.getAttribute("cpdc_primarypracticearea").setRequiredLevel("required");

     }

}