Lines cut & paste

[masvil]

I have 2 text file.

file 1:

(line1)BEGIN: bla bla

(line2) bla bla bla

(line3)END

(line4)

(line5)BEGIN: bla bla bla

(line6)bla bla

(line7)bla bla bla bla

(line8)END

(line9)

(line10)BEGIN: this part of log

(line11)is not finished yet

(line12)so leave it here

file 2 is empty

After a script (that I'm trying to write without any good result) they should have to be so:

file 1:

(line1)BEGIN: this part of log

(line2)is not finished yet

(line3)so leave it here

file 2:

(line1)BEGIN: bla bla

(line2) bla bla bla

(line3)END

(line4)

(line5)BEGIN: bla bla bla

(line6)bla bla

(line7)bla bla bla bla

(line8)END

(line9)

I hope I was clear. Any help?