"last modified" from first Post of a Thread

[DuNkLeArChOn]

Hey,

I edit the threadbit-template currently and i want to show the time of the modifikation of the first Post of a Thread. My Forum is a Tutorial-Overview. If a user refresh his Tutorial, i would like to show this in the Threadbit.

how can i do this ?

with

{vb:raw thread.lastposttime}

i got the last time of a posting inside a thread...

but how do i get the time of "last modified" of the first post of the thread?
is it like this code ? :

{vb:raw thread.lastmodifikation}

please help :-)