Definitely it is not a straight forward approach, and you might need little bit of tweaking around with the comment field. Please find attached eg file which i tried might be of any help. Based on my assumption thinking that the Reg numbers in the comment field will be seen after the word 'For'. Taking this as a consideration i have done a workaround.
I did attached the file. However, as said i have used For word to get the Registration Numbers so you can ignore that then. Just wondering did you try crystles if condition?? Did you get what you are looking for.
Yes I thought about putting the trim on the comments section, but I did not think it would matter as much since I was doing a Wildmatch. Trimming the comments field wouldn't have any advantage I think, but it could help find the Code faster.