I think that you might be selecting the wrong option in DPP to set a custom WB. Also, you can't normally change the extension of a file type to make it work. The *.VRW is a scripting language file (sort of like an XMP or TXT file type) while the CR2 is a binary image file. I have the impression that you are selecting the <Import> button and have changed the extension on a CR2 image of a gray card to make it a VRW file. If so, that is not the correct procedure. Here is the procedure for creating a Custom White Balance in DPP:
- Shoot an image of a reference card (either x-rite, gretagmacbeth, expo disc, WhiBal, sheet of white copy paper, or a high quality 18% reflectance gray card)
- In DPP, use the eyedropper or color wheel or the color temperature to set a custom WB.
- Next, click the <Register> button.
- Instead of clicking on the <Import> option, click on <OK>.
- It should then be registered as personal custom white balance 1.
- I am not a DPP expert, so I don't know if it can be given a unique name since the drop down menu is for shooting styles and not just white balance.
- Possibly you might be wanting to use Canon's Picture Style Editor. You start with one of the existing styles and then modify it with your own WB, etc. You can then save it with a name of your choice.
Hopefully this is what you are looking for. Note that just like color temperatures, this setting will only be good for the same lighting conditions as the shot made for the reference card.
Everybody's preferences are different, but for me when it is important, I will just shoot two pictures -- one with a WhiBal card or an x-rite card and another without the card. Most of the time, I use AWB and then use personal judgment in post processing to adjust WB if I feel that it needs tweaking.