webinject - dealing with popups

Hello

We have a webapp that launches a link in a popup. We need to use webinject to check the content of that popup but have been so far unsuccessful. We use webinject as a nagios plugin.

Does anyone have any experience of using/configuring webinject and know if this is possible or not?

Otherwise, does anyone know of another (free?) tool that can do the same job?

Thanks

Steve.

check if Selenium is useful in this case