What is your OS? And your mouse? Todays Logitech have a setting for speed in games, copuled with ddraw setting in dosnox.conf should make it adjustable.

Ohm missed to give more Information:
My primary System is Waindows 7 and a Logitech M500 (USB).
But I installed DosBox in i virtual WindowsXP (Vbox). (I use XP for games and testings, that W7 is not messed up with installations and so on)

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Oh vergessen.
Mein System ist eigentlich ein Windows 7, die Maus eine Logitech M500 (USB).
Aber ich habe DosBox in einem virtuelen XP installiert.
Das verwende ich imer zum Testen und Spielen um mein System nicht unnötig zu verunreihnigen.

DOSBox isn't supported in a VM. Run it on your host.

and if you're paranoid about install programs and registry clutter, don't be. DOS games don't do that, and Dosbox doesn't necessarily require that either.

abstracting DOSBox through a VM will just make your DOSBox experience worse. It runs fine on W7.

So, start up Logitechs SetPoint software and play with the mouse settings, especially the advanced ones. But really don't run dosbox in a virtual machine. You CAN but then you need to keep all bug reports to yourself since it is not supported and is probablythe cause of a couple of other problems.

In DOSBOX settings,

[sdl] -> autolock=false

The solution has solved the problem.