portfolio "geometric" annual return

clearlycanadian

Say ... a portfolio with 2 stocks (50-50). For the 2 stocks, I have their 3-yr geometric annualized returns. How do I find the portfolio 's 3-yr geometric annualized returns?

we all know it's not the weighted average of the 2 stocks' geometric returns. I've googled, but only found "approximation". Anyone knows the formula? (Excel command is even better)

Thanks

Windjam

Can't you just convert each geometric return to a holding period return, then use the weighted average to get a portfolio return, then re-convert it to a geometric return?