problems with text box

[lore_flo]

be patient with me, I am a beginner with NSIS.
I am using MUI
I have created a new form and I have inserted in my form some text boxes. Then I have declared a variable and in the function that shows my form, I have read one of my text box, using the macro MUI_INSTALLOPTIONS_READ. But unless I change the content of my text box, the variable content doesn't change. What is my error?
this is my code:

Function CustomPageA

!insertmacro MUI_HEADER_TEXT "A - Dati del Cliente"
!insertmacro MUI_INSTALLOPTIONS_DISPLAY "cliente.ini"
!insertmacro MUI_INSTALLOPTIONS_READ $ABC "cliente.ini" "Field 30" "Text"

;Display a messagebox if check box was checked
StrCmp $ABC "ABC" "" +3
MessageBox MB_OK "Hai scritto ABC!!"
Goto +2
MessageBox MB_ICONQUESTION $ABC ;"--> N O N <-- Hai scritto ABC!!"
FunctionEnd

thanks for any error.

[Red Wine]

I guess you're reading a text field,
to do so you need to read the STATE of the field not the TEXT in custom page leave function.

[lore_flo]

Thank you.
I have another question (common for a lot of beginners, I think): there are pubblications that explains these elementary things? The manual is complete, but it is difficult (at least for me...) to discover the correct sintax of the various command in a effective environnment.

[Red Wine]

I'd suggest as 1st step the combination of manual along with included examples, by my opinion this is an excellent way to get familiar with NSIS environment.
As for next step should be wiki at http://nsis.sf.net where you'll find tons of code from simple snippets to the most advanced scripting experience.
Of course there's always this forum where you get top level support either by using the search feature or by posting your query.