Batch file to remove lines above and below certain phrase

Question

I rent a piece of software which saves docs in a textfile.

Each question is formatted into clusters, with a label in square brackets, followed by a list of values associated to that question, following on separate lines, as per excerpt below:

[Q1]
Answer = yes
Source = A
Value = 20

[Q2]
Answer = yes
Source = B
Value = 20

[Q3]
Answer = yes
Source = A
Value = 20

What I would like to do is strip out any complete blocks of text where Source = B, so that the outputted text file of the example above would read as:

[Q1]
Answer = yes
Source = A
Value = 20

[Q3]
Answer = yes
Source = A
Value = 20

Basically omitting

[Q2]
Answer = yes
Source = B
Value = 20

Can this be done? if so, what is the best method

Answer 1

The Batch file below was written precisely to solve this problem as it is stated, so it will not solve any other similar problem.

@echo off
setlocal EnableDelayedExpansion

set "Source = B"
for /F "delims=" %%a in (input.txt) do (
   set "line=%%a"
   if "!line:~0,1!" equ "[" (
      if "!Source !" neq " B" (
         echo !label!
         for %%v in (Answer Source Value) do echo %%v =!%%v !
         echo/
      )
      set "label=%%a"
   ) else (
      set "%%a"
   )
)
if "!Source !" neq " B" (
   echo !label!
   for %%v in (Answer Source Value) do echo %%v =!%%v !
   echo/
)