If I have a portfolio with, for example, a return of 5% and standard deviation of 7% how can I graph a growth of a thousand yearly over 40 years? Also, how can I graph the same chart but with an 80% confidence interval?

I think I know how to do the first part: make a table with =NORM.INV(RAND(),.05,.07) in one column and then multiple down in the next column by 1+ the calculated return, however I'm stuck on how to find what the portfolio can expect to return with 80% confidence. Can anybody help?

Please let me know if I can provide anymore information.