Hello,
Unfortunatelly you can't use Group Policy Preferences.
You can use a logon script that disconnect the drive and reconnects the drive.
Just use gpedit.msc:
http://systemmanagement.ro/blog/2008/12/15/group-policy-user-configuration-logon-script/
The script would be like:
net use m: /delete
net use m: \\server\share1 /persistent:yes
MVP Group Policy - Mythen, Insiderinfos und Troubleshooting zum Thema GPOs:
Let's go, use GPO!