  A financial market model with general semimartingale asset-price processes
and where agents can only trade using no-short-sales strategies is considered.
We show that wealth processes using continuous trading can be approximated very
closely by wealth processes using simple combinations of buy-and-hold trading.
This approximation is based on controlling the proportions of wealth invested
in the assets. As an application, the utility maximization problem is
considered and it is shown that optimal expected utilities and wealth processes
resulting from continuous trading can be approximated arbitrarily well by the
use of simple combinations of buy-and-hold strategies.
