Hide a field dynamically according to another selection field

Hi,

For a search screen, I am trying to hide a field dynamically according to another selection field.

I tried to use the steps provided in the following discussion, but the outcome is not seen on the screen.
community.sagecrm.com/.../28799.aspx

Custom Content script I used
================================
<script>
crm.ready(function(){
crm.fields("comp_siteid").hide();
})
</script>


OnChangeScript I used
================================
if(this.value=="Site"){
crm.fields("comp_siteid").show();
}

I am using "Sage CRM 7.2.e.3" and The field I am trying to hide is of type "StoredProc"

Seems simple, but I am not sure what I am missing.

Thank you
Satheejan