jQuery Grid Plugin - jqGrid

Hello,

how can I make dynamically checkboxes and dropdowns editable using JQGrid with asp.net?

I have this code:

<trirand:JQGrid runat="server" ID="JQGrid6" AutoWidth="true" Height="232px" DataSourceID="sql" OnRowEditing="JQGrid6_RowEditing"><trirand:JQGridColumn DataField="column" Editable="true" EditType="DropDown" EditValues="J:Ja;N:Nein" HeaderText="Gesamt" />                             

<trirand:JQGridColumn DataField="column2" Editable="true" HeaderText="Schwelle" />

 <trirand:JQGridColumn DataField="column3"  Editable="true" EditType="DropDown" EditValues="J:Ja;N:Nein" HeaderText="RundenPP" />

...

</trirand:JQGrid>

Whether a Textbox/Checkbox/DropDown must be editable or not, depends on the values from the column. So I need an event which is called before the grid JQGrid6 is shown where can I make some validation. There would be OnLoad, OnPreRender, OnRowSelecting events. The problem is, that I have no access inside this events to the data of the cell. Only in OnRowEditing I can access the actual values, but it is to late, because the Textbox/Checkox/DropDown would be editable before the event is fired.

Can anyone help?

Best regards