How to narrow down the drop down menu based on other drop down selections?

Hi,

Is there a way to narrow down the big drop down selection based on other drop down selection?, I have 5 drop down menu's, lets say A,B,C,D and E is big drop down. I am looking for a way to narrow down the 'E' based on 'A','B','C','D' selection. 
The value's or entries in E, i wrote them in .SUD file.

for example: "3029-F4-HD-RWNS-X-JK" , is one of the entry in drop down 'E'. the functionality i am aiming for is, 

on selection of Drop down 'A', it should narrow down the drop down selection of 'E', containing R at that specific position

similarly with other 3 drop downs,
Drop down B should interact with letter W

Drop down C should interact with letter N

Drop down D should interact with letter S

Can we accomplish this using regular expressions?

 Thanks in advance.