I would like some clarification and suggestions for acting the part of Lady Macbeth as she receives the letter in Act I, Scene v of Macbeth.I've...

First, I must say I really admire your scholarship and
your dedication to excellence. These are fine characteristics in a student, and I'm sure
your drama teacher will soon realize what a prize he has in you! That said, let me see
what I can contribute to your cause.

Let's look at the
particular lines you mention:

readability="13">

Thou'dst have, great
Glamis,

That which cries "Thus thou must do" if thou have
it;

And that which rather thou dost fear to
do

Than wishest should be
undone.

To interpret this
passage, consider it in the context of the scene. Lady Macbeth obviously is set on fire
with ambition when she reads the letter. Then she starts assessing her husband's
character, which she knows very well. She knows he will want the crown, but she also
knows that his nature is full of "the milk of human kindness," which will make it
difficult for him to do what must be done to become king quickly ("to catch the nearest
way.") This observation makes it clear that she is already thinking in terms of
murdering Duncan. Macbeth will want to be king, but he will not want to commit
murder.

Now to the lines in question. In them she is still
analyzing Macbeth's nature; also, she may be rationalizing what she already knows she
will do--push him into murdering Duncan. She is saying that Macbeth will not want to
kill Duncan and that he will be afraid to do so, but that once he follows through, he
will not be sorry and will not wish his actions
"undone."

As for portraying her in terms of her emotions,
as she reads the letter, she would probably feel a growing sense of excitement as she
begins to realize what it says and what possibilities it suggests. Notice her first
reaction after finishing the letter:

readability="7">

Glamis thou art, and Cawdor, and shalt
be

What thou art
promised.

Her mind is made up
instantly and there is no reservation: Macbeth will become king. The following line
begins her evaluation of his nature and makes it clear that she will not wait for his
destiny to arrive; she will see that it happens now.

In
blocking, there are three shifts that occur within the
scene:

• There is a natural break between her
  finishing the letter and responding to it.


• Then there is
  a second emotional break between stating that Macbeth "shalt be" what he is promised and
  her concerns about his personality. This one is signaled by the word
  "yet."


• The third emotional shift occurs when she says
  "Hie thee hither" and  lays out her intentions to override Macbeth's anticipated
  hesitation and disabuse him of "[a]ll that impedes thee from the golden round (the
  crown)."

From the time she reads the letter
until she concludes her soliloquy, Lady Macbeth's mind moves through several stages of
comprehension and decision making, and her emotions change with each realization. This
is a very dynamic soliloquy. I hope this helps, and good luck to
you!