finding a message's thread level number

is there any way to get a message's thread level
number.

for example:

message A
  message B
    message C
  message D
message E

so,
message A thread level number is 0
message B thread level number is 1
message C thread level number is 2
message D thread level number is 1
message E thread level number is 0

thanks,

paras

__________________________________________________
Do You Yahoo!?
Make international calls for as low as $.04/minute with Yahoo! Messenger
http://phonecard.yahoo.com/