Setting value of Inno Setup custom page field from command-line

I have configured the below script to ask the user for an IP address as part of the install wizard, this address gets written to a config file which the application will reference to know where to communicate with. I would like to offer the opportunity to specify this IP address as a parameter in the command line as well so that deployment can be automated and performed silently.

From my research, it seems to be possible to add a command line parameter but I am struggling to understand exactly how to set this up within my Inno setup and then how I can make this optional to allow it to be specified on the command line or through the install wizard.

For example something like app1.exe /ipaddress 192.168.0.1

Apologies if this is an easy process, I am new to Inno Setup so any help would be appreciated.

Can anyone offer any assistance to help me get this setup?

[Code]

var
  PrimaryServerPage: TInputQueryWizardPage;

function FileReplaceString(ReplaceString: string):boolean;
var
  MyFile : TStrings;
  MyText : string;
begin
  Log('Replacing in file');
  MyFile := TStringList.Create;

  try
    Result := true;

    try
      MyFile.LoadFromFile(ExpandConstant('{app}' + '\providers\win\config.conf'));
      Log('File loaded');
      MyText := MyFile.Text;

      { Only save if text has been changed. }
      if StringChangeEx(MyText, 'REPLACE_WITH_CUSTOMER_IP', ReplaceString, True) > 0 then
      begin;
        Log('IP address inserted');
        MyFile.Text := MyText;
        MyFile.SaveToFile(ExpandConstant('{app}' + '\providers\win\config.conf'));
        Log('File saved');
      end;
    except
      Result := false;
    end;
  finally
    MyFile.Free;
  end;

  Result := True;
end;

procedure InitializeWizard;
begin
  PrimaryServerPage :=
    CreateInputQueryPage(
      wpWelcome, 'Application Server Details', 'Where is installed?',
      'Please specify the IP address or hostname of your ' +
        'Primary Application Server, then click Next.');
  PrimaryServerPage.Add('Primary Application Server IP/Hostname:', False);
end;   

procedure ReplaceIPAddress;
begin
  FileReplaceString(PrimaryServerPage.Values[0]);
end;