Replacing data at a specific location within a packet

[flyingcookie12]

Hi there, new to ettercap filters and can't find much online regarding this.

Let's say we have a packet with the following data:
0000 28 16 a8 48 fa 76 c8 99 b2 a0 8b e3 86 dd 60 03
0010 a8 f0 05 64 06 38 26 06 47 00 00 00 00 00 00 00
0020 00 00 68 12 06 b7 2a 00 23 c7 51 b7 02 01

How would we target and replace the byte 2a (highlighted in bold) with a different value?

Any help would be appreciated.
Thanks

[LocutusOfBorg]

from etter.filter.examples file:

# some operation on the payload of the packet
if (DATA.data + 20 == 0x4142) {
   DATA.data + 20 = 0x4243;
} else {
   DATA.data = "modified";
   DATA.data + 20 = 0x4445;
}