You will need to select the device type to Foundry.Switch.General. I can't say that this will definitely work with your device but it's the only Foundry based script we have at the moment so it's your best bet. Assuming the script logs in OK you will then want to set up a Device.CLI.Send commands general activity to send the 'clear ip cache' command and schedule this to run at the interval you require.
If the Foundry.Switch.General script does not work for you please create a device capture file. 'File|Enable capture mode' in the CatTools menu and then run the activity against the device in question. In the debug folder in the main CatTools folder you will then have a debug log detailing the interaction between CatTools and the device. **** out any sensitive info and post it back here in a zipped attachment and I'll have a look at it.