Thank you, but SaveDefinitions is an option of Manipulate and i don't use that function...

A very small example of what i mean:

Button["Create an energy calibration",
 fit = CreateDialog[
    Column[{"Insert a pair of point like {voltage,energy}", InputField[Dynamic[pointcal]], Button["Proceed",
       fit = Fit[pointcal, {1, x}, x];
       DialogReturn[fit]
       , ImageSize -> Automatic]}]];
 ]

The user clicks on this button and inserts the required data and the computation is performed. This is a simple example, so if i hide the code with the cell on the right it works, but for more complicated codes is fore difficult and it is always not "safe" as i wrote in the previous post (with an error the code appear)

Thank you

Andrea, designing a Mathematica application is a good idea. If you are interested in a guide to how to design a pretty much standard application look at A Mathematical Style at my web site.

I would be wary of writing notebooks for others that are just buttons and dynamic displays. It might be better to write 'literate' notebooks that have textual discussion mixed with the displays and look more like a paper. Most dynamic displays are not that self-explanatory.

A second method for hiding code, beside double clicking on the cell bracket, is to use the Mathematica Menu, Cell, Cell Properties/ Open command. (Alt+CPO) This semi-permanently closes a cell. The reader can open it if he wishes but normally it will stay closed, even between sessions. One advantage is that you can have textual discussion, hidden code, and then output so the notebook reads like a paper. Another advantage is that most code for many displays, such as graphics or dynamic displays, is one-off and it's very convenient to put it just where it's used.

The disadvantage is that the closed cell is very narrow and readers might miss it and not evaluate it. My solution to this was to design an 'Eval' button, which I insert in a Text cell before the code that automatically evaluates the code cell, keeping the cell shut. I have an application, Presentations, which is a help in writing literate notebooks. There is a button on the Presentations palette to paste the Eval button into a notebook so it's very convenient and I use it a lot. If you would like a copy of Presentations write me and introduce yourself and I'll send you a link.

Another technique with complicated displays is to put them in windows (which you already know how to do) that can be positioned next to the notebook. Then if there is a lengthy discussion in the notebook it can be scrolled without losing sight of the associated display.

Thank you David, you gave me some useful ideas! The simple option of "open cell" seems powerful, and there is no problem with the missing of the cells because there will be ever a button to evaluate it!

I understand and share your opinion about an only-graphics application, in fact, my idea is that there will be some text explanation but i don't want to show the code to users, because it's not necessary and can cause problems...

As soon as possible, i'll send you an email for the presentation.

If i include a Print function in the code, every time i evaluate it a new output cell is created. Do you know how to force to update the previous output with the new one (to create only one output cell)?

Thank you Kuba, but the application can't be included in one or more Manipulate functions

Andrea,

If i include a Print function in the code, every time i evaluate it a new output cell is created. Do you know how to force to update the previous output with the new one (to create only one output cell)?

Look at PrintTemporary[] -- You can replace a print with a new one and control the display of information. For example, you can print some update information and clean it all up at any point.

Regards,

Neil

Thank you all for your advices! I'll try to put them into practice.

@David: I have sent you an email for the presentation