Confidence interval

Hello,
I'm trying to calculate the confidence interval of a variable TVh (Tree volume / hectare ).

TVh is given by the product of TH Tree Density (Trees/hectare) and tMV Trees mean volume of sampled trees.

TVh = TH * tMV


How can I calculate confidence interval of TVh?

Thanks.

Well, you'll need a few hectares with trees. With what sort of data are you working?