How to redirect old .htm page to new .htm page?

How to redirect old .htm page to new .htm page? IIS Server - Shared Hosting. My web hosting company says although there is setting in the control panel of IIS but because we have a shared hosting account, we are unable to modify the server settings as this is a shared hosting accounts. However using custom scripting you may also accomplish this. It know scripts that would redirect .asp, .php etc pages. But what about old .htm page (http://www.domain.com/abc_123.htm) to new .htm (http://www.domain.com/abc-123.htm) page. Can anyone help me ? Its urgent. Thanks in advance.