Determining where a message came from

[Mikey]

Is there an easy way to determine if a message is being generated by
it being typed into the message box as opposed to being executed in a
script?  I realize I could pass an optional parameter, but I didn't
know if there is some property that is set that I could check.


-- 
On the first day, God created the heavens and the Earth
On the second day, God created the oceans.
On the third day, God put the animals on hold for a few hours,
   and did a little diving.
And God said, "This is good."