Combining data is Access is certainly possible, but to make sense, there
needs to be some key field in both the contacts and the calendar data that
can be used to link the two sets of data together.  I doubt that there are
fields in both sets of data that would contain the necessary information for
linking by default.  It would probably be possible however to preface and
entry into a particular field with an identifier that would allow the
linking to be accomplished, though it may be a two step process - a pair of
queries to get at the indentifiers by themselves using the Left() function
and then the other to link the queries together based on the exposed
identifiers.

And then, once you are using Access, it may well be better to use a report
in Access to produce the result rather than involve mailmerge.