This is how i finally did it:
[Code]
{ https://msdn.microsoft.com/en-us/library/windows/desktop/ms645505.aspx }
{ Use Windows MessageBox() function as an MsgBox() replacement. }
{ MessageBoxW is the UNICODE version of this API call. }
const
{ these are not exported in Inno Setup! }
MB_ICONERROR = $00000010;
MB_ICONWARNING = $00000030;
MB_ICONINFORMATION = $00000040;
MB_ICONQUESTION = $00000020;
function _MessageBoxW_(hWnd: Integer; lpText, lpCaption: String; uType: Cardinal): Integer;
external 'MessageBoxW@user32.dll stdcall';
{ Usage: SysMsgBox('Error', 'Shit happens!', MB_OK or MB_ICONERROR); }
{ res =: SysMsgBox('Question', 'blah blah', MB_YESNO or MB_ICONQUESTION); }
function SysMsgBox(const Caption, Message: String; const Flags: Integer): Integer;
begin
Result :=
_MessageBoxW_(StrToInt(ExpandConstant('{wizardhwnd}')), Message, Caption, Flags);
end;
Thanks to all for your help!