Using Inno-Setup for Excel Add-In Installation

Recently, I came across a need to write an installer for Excel Add-In. I found a sample of installer written using Setup-Factory at (http://www.jkp-ads.com/articles/AddinsAndSetupFactory.asp) and that was my main inspiration source to write this in Inno-Setup. My current code is not completely cleaned up and doesn't include an option for adding the Add-In in the [Add-In Manager] registry key but it should do its job well. Here is the setup script:

[Setup]
AppName=My Excel Add-In
AppVerName=My Excel Add-In ver 1
DefaultDirName={pf}\Durlabh
[Files]
Source: MyExcelAddIn.xla; DestDir: {app}; AfterInstall: CheckRegistry(true);

[Code]
procedure CheckRegistry(Install: Boolean);
var
  OfficeVersions: TArrayOfString;
  I: Integer;
  J: Integer;
  Installed: Boolean;
  Key: String;
  Value: String;
  Keys: TArrayOfString;
  AlertMessage: String;
  CurrentValue: String;
  NewKey: String;
  KeyNumber: Integer;
  NewKeys: TArrayOfString;
begin
  // Location of Add-In
  Value := ExpandConstant('"{app}\MyExcelAddIn.xla"')

  // List office versions
  if RegGetSubkeyNames(HKEY_CURRENT_USER, 'Software\Microsoft\Office', OfficeVersions) then
  begin

    // Check all the office version
    for I := 0 to GetArrayLength(OfficeVersions)-1 do
    begin
    
      // Initialize Installation Info
      KeyNumber := 0;
      Installed := false;
      
      // Check if Excel is installed and has Options
      Key := 'Software\Microsoft\Office\' + OfficeVersions[I] + '\Excel\Options';
      if RegKeyExists(HKEY_CURRENT_USER, Key) then
      begin
      
        // List all the add-ins currently being shown - for this read all value name
        if RegGetValueNames(HKEY_CURRENT_USER, Key, Keys) then
        begin

          // Process each value name
          for J := 0 to GetArrayLength(Keys)-1 do
          begin
          
            // Check if it is really an ADD-IN
            if (Length(Keys[J]) >= 4) AND (Copy(Keys[J], 1, 4) = 'OPEN') then
            begin

              // Read the add-in path
              if RegQueryStringValue(HKEY_CURRENT_USER, Key, Keys[J], CurrentValue) then
              begin
              
                // Check if it is the add-in we are installing
                if CompareText(Value, CurrentValue) = 0 then
         Installed := true
        else
                begin 
        
          // Store all other add-ins in another array
          // Will be used for uninstall
                  SetArrayLength(NewKeys, KeyNumber + 1);
                  NewKeys[KeyNumber] := CurrentValue;
                  KeyNumber := KeyNumber + 1;
                end
       end
      end
     end
    end
    
    
      if Installed then
      begin
        // Are we trying to uninstall?
        if not Install then
        begin
        
          // Re-serialize all other add-ins
          for J := 0 to KeyNumber-1 do
          begin
            NewKey := 'OPEN';
            if J > 0 then
              NewKey := NewKey + IntToStr(J);
            RegWriteStringValue(HKEY_CURRENT_USER, Key, NewKey, NewKeys[J]);
          end
          
          // Delete additional keys
            repeat
            NewKey := 'OPEN';
            if J > 0 then
              NewKey := NewKey + IntToStr(J);
              
          until (Not RegDeleteValue(HKEY_CURRENT_USER, Key, NewKey))
        end
        AlertMessage := 'Installed'
     end
      else  // Not installed
      begin
        // We are trying to install - add to the last
        if Install then
        begin
          NewKey := 'OPEN';
          if KeyNumber > 0 then
            NewKey := NewKey + IntToStr(KeyNumber);
          RegWriteStringValue(HKEY_CURRENT_USER, Key, NewKey, Value);
          end
          AlertMessage := 'Not-Installed';
      end
        AlertMessage := 'For office version ' + OfficeVersions[I] + ', add-in is ' + AlertMessage;
      //MsgBox(AlertMessage, mbInformation, MB_OK);
      end
    end
  end
end;

procedure CurUninstallStepChanged(CurUninstallStep: TUninstallStep);
begin
  case CurUninstallStep of
    usPostUninstall:
      begin
        CheckRegistry(false);
      end;
  end;
end;

Your comments/ feedback will be highly appreciated.