I don't think that'll work, from looking at the packets it seems that you just send one saying what you're attacking, then the game does the processing on their server and sends you back the result of the battle, how much health and gold and exp you have afterwards, etc.
I could be wrong of course.
As for learning how to do it, It's always bothered me that there isn't a tut on this site for how to use the filter feature of WPE Pro correctly. I might write one eventually, but for the time being, here's how you would (for instance) make it so that you always attack the training dummy when you attack any one-digit monster.
1. Fire up WPE Pro
2. Go to target program in the upper right and select whatever browser you're using (IExplorer, firefox, Opera, etc.).
3. Go to view, select options, and uncheck Sendto and Recvfrom (some people also uncheck Recv, but I like to keep it there so I can see what's being returned)
4. Press the little play button above the dials.
5. Attack something in-game (I attacked a Strangler Crab because I'm a low level noob)
6. Go back to WPE Pro and click the red stop button. A window should pop up with a bunch of packets in it. Scroll through these until you see a Send packet with POST as the first word (this means you're actually sending some data over there).
7. Click this packet and resize the window so you can read through it. If you read through, it carries 4 important pieces of information:
A. What you post to (in this case /inc/act/attackscript.php)
B. Where you came from (in this case
http://www.eternalwars.com/inc/
act/act.php)
C. Who you are (represented by the cookie PHPSessionID, which appears
to be random)
D. What you're attacking (represented by the code monstername=4)
Now, having identified what information is carried, think about what to change. Changing what you post to just means you didn't attack, Changing where you came from will either change nothing or produce a bug, and you cookie is randomly generated so you wouldn't be able to change that to a valid value. So, for this particular packet, all you could change that would do anything is what monster you're attacking.
8. Now to create a filter to do this. Double click filter1 over on the left, change it from normal to advanced (under mode on the right), and then change it to start modifying "from the position of the chain found" (you have to switch to advanced mode before you can change that).
9. You want to search for the code "monstername=" and replace whatever comes after it with the number 1. To do this, start editing the top box where it says "search" to be the hex equivilent of monstername= (WPE Pro conveniently tells you this in your packet, it's 6D 6F 6E 73 74 65 72 6E 61 6D 65 3D)
10. You'll notice that 3D goes into the box 012. To edit the number right after 3D, or = in normal text, we go to +012 in the modify box below search (+0 is 1, +1 is 2, etc. so +12 is the 13th box, or the number we want to edit) and put in 31. 31 is the number 1, 32 is the number 2, 33 is the number 3, and so on.
11. Change the name to something like Monster edit and and press apply. Now, check monster edit under filters, and press the big ON button between the pencil and the big X above it. Now go attack some one digit monster (like a Strangler Crab) and see what happens.
12. Did you attack the training dummy instead? If so, it worked. If not, reread this and see what you did wrong.
After doing that, you know enough about filtering to see if any other features are exploitable.
Blocking packets might also be viable (you'll notice a checkbox named block when making a filter), like for ignoring duels or something, but probably not for avoiding damage in a normal fight.
