[Urgent] Custom page to display error information and quit installation

I am checking for prerequisite before unziping files to a directory (check version of software installed, read registry key...).

I need a custom error page to add a link to a web site to download the required software.

I do all the checking in my main section and jump to a label InvalidVersion: when prerequisite is not met.
My problem is to display my custom page at this point and then quit the installation.
I am using MUI.

I try to add Page custom InvalidVersion
!insertmacro MUI_PAGE_WELCOME
Page custom InvalidVersion
!insertmacro MUI_PAGE_INSTFILES
!insertmacro MUI_PAGE_FINISH

In .OnInit I have the following :
InitPluginsDir
!insertmacro MUI_INSTALLOPTIONS_EXTRACT_AS "InvalidVersion.ini" "InvalidVersion"

Then I have the function definition
Function InvalidVersion
!insertmacro MUI_HEADER_TEXT "$(WRONGVERSION_TITLE)" "$(WRONGVERSION_SUBTITLE)"
# Display the page.
!insertmacro MUI_INSTALLOPTIONS_DISPLAY "InvalidVersion"
FunctionEnd

in the main section I try to display the custom page by calling the function :
Call InvalidVersion

My problem is that no button is available to quit the installation ! Next and Back buttons are greyed out.
I would like to only have one button which would be "OK" and that would quit the installtion.

Here is my InvalidVersion.ini
; Auto-generated by EclipseNSIS InstallOptions Script Wizard
; 16 janv. 2007 17:03:07
[Settings]
NumFields=1
NextButtonText="OK"
[Field 1]
Type=Label
Left=67
Top=63
Right=242
Bottom=72
Text="Some Text\r\n"

You can not call a page from a section.
Sections executed within InstFiles page.
You need to do all the checking in a function preferably within the custom page's function before display the page and according to checking skip or display the custom page and add Quit when OK is pressed