Run a script when a VPN user logs inn and update DNS

RouterOS Scripting
1

When a VPN user logs inn, MikroTik sends out a log like this:

pptp,ppp,info,account MikroTik: Hanson logged in, 192.168.2.5

I did try to search the board to find something that could help me, but did not find.
What I do like is to add a static entry to my DNS like this:
IP: 192.168.2.5
DNS: VPN-Hanson

If the DNS entry already exist, over write it.

This would help me to get better statistics in my Splunk prosjekt.