LabView's formula nodes support exp(x) and ln(x). If those are the functions you need, just include them in the formula you feed to Formula Waveform.vi.
If you need to use e directly, you could get the e constant from the Numeric >> Additional Numeric Constants palette, then convert it to a string using Number to Fractional String on the String >> String/Number conversion palette, concatenate it with the reset of your formula, then feed that string to Formula Waveform.vi.
