No need to sandblast. What Barry recomends and has worked well for me and others is very simple. Mask off around the area you want white so as to protect the chrome. Sand with 180 grit. Probably by hand judging by the small area but if you can get a DA in there that would be ideal. Sand until you have scuffed it completely. Then spray at least 2 coats of SPI Epoxy (the best, really no equal on the market today). It needs to be epoxy not urethane or acid etch. Then proceed as you would with any primed surface. Ideally I would let it sit in the sun for a day, come back and wet sand it with 400, shoot one reduced coat of epoxy (1:1:1) as a sealer to promote adhesion, then proceed with color, be it a basecoat or single stage white, and finally clear it if using base.
This has been done many times by many people and as long as you are using SPI Epoxy and follow those steps, adhesion to the chrome will not be an issue.