The problem has to be either this line:

Application.SendKeys "^(b)", True

or this line:

Application.SendKeys "^(a)", True

I'm not really sure why they are even in the macro from what I can see in your code. Usually that command is used to force a command into a different program than Excel (say a DOS macro).

Try putting an apostrophe (single quote: ' ) in front of the lines to make them into comments for testing purposes.