C++ question

[Donkey]

My boss is writing a program to control some equipment using C++. it needs to talk out of the com port several times during a loop but it doesn't seem to like it. If you just run the code outside of the loop (i.e. once) it runs fine. Inside the loop it will also only do it once and he can see (by some blinky lights on the equipment) that the communication is lost whilst it is in the loop. it only does the one command when the loop is finished.
Is there a command in C++ which forces it to do any waiting commands instead of buffering them. like the Doevents command in VB?
Any ideas?
Rod