Sorry, but Captivate doesn't yet have any capability for
this. You might see if the software that came with your Webcam has
a function for recording video. What you would need then is a way
to make that video a .FLV or .SWF file.
You might also wish to investigate a different Adobe product
called Visual Communicator 3. This product seems to allow recording
from WebCams and camcorders.