Try and stop thinking like an aspx developer :) and start thinking like a DotNetNuke developer

A DotNetNuke module is made up of one or more 'controls'.  Each control has a 'key'.  The default control (usually the 'View' mode) has a blank key. To direct a user to the edit control for a specific data item, create a new ascx control and in the module definition page create a new 'control' give it a key, for example 'Edit, and then tell it where your .ascx file is that you want to associate with that control key'. To display your new control, you would use the NavigateURL() method which takes some parameters like which control key to display and any data you want to pass to the control. 

It sounds complicated, but once you understand the 'control' concept, it saves you a lot of work and makes it easy to write modules with multiple 'views', or as DotNetNuke refers to them, 'controls'.

Start by looking at the code for a simple core module like Links which has a display control and an edit control. Look at the Module Definition and see how the controls are defined. Then look at the code behind and see how the link is crafted to take the user to the edit control.

If you are still unsure after looking at the Links module, let me know and I can post some sample code and screen shots to step you through it.