As you have a 940 put the Fiat Blue Me Navcore on it and you will get all the truck related options as if by magic The Navcore is available straight from the server at TomTom by clicking
The Blue Me Version
A quick word of caution before you install this, in the root of the download there is a file named "system" which is just under 1 MB in size, deselect this prior to extracting the files to the device or MicroSD card, if you don't do this your bootloader will get incremented which isn't possible to undo, the bootloader uplift isn't needed to get this working on a 940.
For more information on this click
Here which also contains a You Tube video link you might be interested in but please read the whole thread BEFORE you jump in and mess up your 940 - Mike