Script Extension - Operation parameter and User form both showing

i created an extension and i have a following xml setup

 

<Parameters>
<Parameter Name="Page"/>
</Parameters>

 

<Columns>

...

<Column Name="Value" Editable="True" EditorType="Parameters"/>

...

 </Columns>

 

<Events>
....
<Event Name="OnSetup" Routine="verifyScreenShown_OnSetup"/>
</Events>

 

Here's the code for the onSetup for form:

function verifyScreenShown_OnSetup(Data)
{
var frm =UserForms.frmVerifyScreen();
if (frm.ShowModal() != mrOk) {
return false;
}
Data.Alias = UserForms.frmVerifyScreen.txtScreenName.Text();

return true;
}

 

The problem is when a click VALUE field is first show the form then Operation parameter form, i expect the it will only show operation paramer on clicking VAlue field while the form on ther fields