awk, how to convert hex to decimal

[Greg Strockbine]

How do I convert a hex number (or is it string) into decimal?

Here is the problem, I take a snap shot of a hex dump from a debugger,
use sed to extract the line I'm interested in, then pass it to awk.
So I've got this field 930A and use the awk substr to break this into
2 fields, a=93 and b=0A.  So that's 2 hex numbers represented as strings
but I want to print the 93 out as a decimal number and I want to use the
0A as an index into an array of messages so I can print out a corresponding
message.
Can I use an associative array for the messages and say something like:
usr_msg = messages[0A]?

How do I convert the 93 to decimal?

Thanks in advance.