Yes, this is possible, just use an INPUTFIELD.
In order to do this you first need to designate a field as an inputfield in your script. Like so...
'' as [FieldName]
FROM Data.qvd (qvd);
Then you can put that field into a straight table. Beware this will wipe your data when you reload and I believe the data you write in will be stored in either the dashboards '.shared' or '.meta' file and will be unique to that user, like an un-shared bookmark.
Just be careful how you input data, you can input into a box that doesn't display all of the component chart and it will split that values down beneath it.
For additional reading try these links for a comprehensive description...
Although, saying this, I also agree with the previous comments that QlikView isn't a great tool for data input and this solution can be a bit clunky. But, if you need the functionality, there it is!
Hope this helps,