Using regular expressions in code generation or regeneration

[raca]

Please look at this code fragment:

#region Custom Code - Generated_Methods
// Generated_Discussion_Methods
public abstract IDataReader GetDiscussion();
public abstract void DeleteDiscussion(int itemID);
#endregion // Custom Code - Generated_Methods

// Generated_NEWCLASS_Methods
public abstract IDataReader GetNEWCLASS();
public abstract void DeleteNEWCLASS(int itemID);

#region Custom Code - Custom_Methods #1
#endregion // Custom Code - Custom_Methods #1

// Custom_Discussion_Methods

I want to achieve 2 things with regular expressions:

FIRST THING: I want to move segment (blank line counts):

// Generated_NEWCLASS_Methods
public abstract IDataReader GetNEWCLASS();
public abstract void DeleteNEWCLASS(int itemID);
to just before line:
#endregion // Custom Code - Generated_Methods
(I BELIEVE STEPS ARE: Find the segment (to be moved) boundaries, copy
it to a variable, replace segment boundaries with empty string and
insert saved text just before: #endregion // Custom Code -
Custom_Methods #1 line")

SECOND THING (this is independent case of the first): If instead of
segment:

// Generated_NEWCLASS_Methods
public abstract IDataReader GetNEWCLASS();
public abstract void DeleteNEWCLASS(int itemID);
I have this segment (let's call it REPLACING_SEGMENT):

// Generated_Discussion_Methods
public abstract IDataReader GetDiscussion(int ID);
public abstract void DeleteDiscussionNew(int itemID, bool Confirm);
public abstract void DeleteDiscussion(int itemID);

I want the corresponding segment between:
#region Custom Code - Generated_Methods
and
#endregion // Custom Code - Generated_Methods
(let's call it REPLACED_SEGMENT):
public abstract IDataReader GetDiscussion();
public abstract void DeleteDiscussion(int itemID);
to be replaced with REPLACING_SEGMENT.
Effectively I want to do code (re)generation where I would like to add
new code segments to existing code (that is preserved using "preserve"
delimiters:
#region Custom Code - Generated_Methods
and
#endregion // Custom Code - Generated_Methods
regions) and later allow for replacing previously generated segment
(which had been moved to "preserve" delimiters I mentioned above in one
of previous generation of code) during regeneration.

Any help would be appreciated.
Rad