Universal Constant

How can I enter the Universal Constant "e" in a formula? (in the same way that entering PI() returns the value 3.14159...)

Thanks for the tip - entered it this morning, and it works fine.
Incidental tip - when entering a complex formula, break it down into more manageable chunks, with the result from each chunk going to a separate cell, then use those (results) cells to construct the final formula, this avoids trying to sort through endless rows of brackets in the formula, trying to find a mistake, if it doesn't produce the required result.