To get e raised to a power, call the Exp function:

Exp(1) ' returns e (2.71828182845905)
Exp(2) ' returns e to the power of 2 (7.38905609893065)

To find pi, call the Atn function, passing the value 1, and multiply the answer by 4:

Dim pi As Single
pi = 4 * Atn(1) ' Calculate the value of pi.