Need help with column searching starting in a grid

I have a website that keeps track of trucks. I have a big table grid full of truck information. We have a column for Model, License Plate, State, and VIN. Each column has a search box at the top where you can type in a character and it searches that column for that character starting at the first character.

My client wants to be able to search the VIN Numbers starting with the LAST 6 digits instead of the first digits. So, say a VIN number is 1HRVDR34TRG12345. He wants to be able to type in a G and it searches for that G in the last 6 digits. Then type in a G1 and it narrows it down even further.

Anybody out there know how to modify dthmlxGrid to do this?