How to set the value of a Workflow Variable in the Task Form of a Flexi Task

Hi,

I am new to Nintex Workflows 2010 and I have worked on some very simple features of the same but now I have the following requirement:

1. I need to keep start a workflow using a SharePoint 2010 List
2. Assign a Flexi Task to a user
3. In the Task Form of the Flexi Task, I need to show the list item in editable mode.
4. On making any changes the changed data should be updated in the SharePoint List.

In order to achieve the above, I have thought of the following method:

1. Create a Workflow Variable each for the list columns that has to be displayed
2. Edit their values in the Task Form as mentioned above
3. Use Update Item and update the values in the SharePoint List one by one.

But the problem in this approach is I am unable to access the Workflow Variables in the task form. Any kind help or suggestion will be appreciated.