Sorry, a little quick with my response.

1) What is the LastActivity variable, and why do you need it? If you need it, then you should probably do something with it (as well as declare it-- you are using "Option Explicit" at the top of all of your modules, right?)

2) At some point you will translate this code into something like...
(warning: this is pseudo code)
[vba]
Set oDocSource = ActiveDocument
'loop through all of the activities in your source document
Do
'get the activity
set rngActivity = FindMyActivity(oDocSource.Content)
'do a bunch of stuff with your activity (splitting into separate testable routines)
rngActivity.Copy
'create your new activity document
set oDocNew = Documents.Add
oDocNew.Paste
oDocNew.Save '(with whatever naming parameters you've done above)
oDocNew.Close
'loop until my search returned the last activity in my source document
Loop Until rngActivity = oDocSource.Content
[/vba]