Modify specific things a txt file

[jesperjes]

Hello

I have now searched all over the net but can't find any good solutions.

Is it possible to modify something specific in a txt file? I have the following file, where I would like to multiply the red numbers by -1. I have many of these files and they all have the same "build up".

My thought was to import the file to excel, modify the numbers and create a new file (or preferably overwrite existing file). But isn't there a way to edit directly in the txt file?

This is what the txt file looks like:

ST
** CQP-10377.nc1
18074
CQP-10377
3
CQP-10377
S235JR
1
PL5
B
2100
1445
5
5
5
0
39.3
2.0
0.0
0.0
0.0
0.0


AK
v 0u 0 0 0 0 0 0
2100 0 0 0 0 0 0
2100 1445 0 0 0 0 0
0 1445 0 0 0 0 0
0 0 0 0 0 0 0
IK
v 949u 1064 0 0 0 0 0
949 1396 0 0 0 0 0
1611 1396 0 0 0 0 0
1611 1064 0 0 0 0 0
949 1064 0 0 0 0 0
BO
v 25s 25 9
v 25s 257 9
v 2075s 1420 9
EN