Linking cells between two workbooks

I would like to link cells in two workbooks such that whenever a change is
made in the source workbook, the destination workbook cell changes as well.
Seems like a simple task in the Help menu, and I followed the directions.
However, although the value in the destination cell changes to the same value
as in the source cell when I hit "Enter", it only works that initial time.
If I go in and make a change subsequently to the source cell, the destination
cell stays the same. If I click on the destination cell, the current value
is shown in the formula field at the top, not the
"=[Book1.xls]Sheet1!$A$1"...type of text that I would expect to see if the
link is working.
Could this possibly be caused by the fact that I have macros running that
effect the source and destination cells? The cells are formatted as times,
and the macro is one that converts an entry like "130" to "01:30"