>I have an idea to make user can modify it's report, but the application should still have control that won't let user to delete the report fields,...
>just to change like the position of report fields, change the font and color and user may add report field
>
>And of course it's all performed in designed mode like We designed it,....
>
>Is there any suggestion,..??

If you give the user the ability to edit reports with the report designer, the user will be able to delete fields.

You could however write a front end frx editor that would allowthe user to change the position of fields on the report by adjusting the report fields corrdinate values directly in the frx. Not helpful visually, but might be your only choice.