home network (win98) with "foreign" pc (win98)

Try installing Ipx/spx protocol on both
systems.

There is no script option available for that. Sadly M$ has not implemented the feature that lets you switch IP settings as you switch hardware configurations. But you can as stated above install NetBEUI or IPX/SPX

I can't change anything on the company network

Use the same ip settings at home as in the company.
Let's say you use 172.16.0.0 with netmask 255.255.0.0 on the company network. The gateway on the company network is 172.16.1.1. You can get this information from the portable using winipcfg.

Win98 caches the ip addresses assigned via dhcp and will use them at home if it does not get a response from a dhcp server.

Now change the ip address on the modem server to 172.16.1.1. That way you will use the modem server as gateway for the portable.

Unless the dhcp lease period on the ip addresses is very short, this should be a viable solution.

Jeg har fundet et sted, hvor løsningen måske findes:
http://www.netswitcher.com/