I ran across some worksheets whose cells contained #name?  It was a minor problem which was easily fixed. But, I wonder if anyone has insight as to how to avoid the problem in the future.

I am reorganizing my vba projects, and moved a module from one project to another.  I recompiled and saved both projects on the server.  The projects are shared by all of my users and are automatically opened everytime a user opens Excel.

Workbooks that referenced the module's function suddenly showed #name?  for intance formulas like
=FirstNumberOrZero(a1).

Strangely enough using Control Alt F9  to recalculate did NOT fix the problem even after closing Excel and reopening it.

But, I forced a "dummy update" by using edit replace to  change all occurances of = to =.  This forced a recalculation that was more thorough than ctrl alt f9, so all of the errors went away.

So, there are several possibilites:
  #1  Excel "compiles the cell" when the cell's formula is first entered, and the compiled version points to the original addin location. Sometimes, this compile causes excel to automatically change =firstnumberorzero(a1) into  ='customfunction.xla'!firstnumberorzero(a1).
When that happens, it is easy to understand why I see the behaviour.  But, in today's example, the function did NOT have the explicit module reference.  I am not sure why, but it appears the explicit reference still existed, it just did not show in the formula.

  #2  Perhaps Excel  does not "recompile the cell" until the cell's formula is again changed.  So, the old spreadsheet was still pointing to the original addin's location?
  if #1 and #2 are correct, it would explain everything.

Of course, a dummy change is not ideal because there are about 20 workbooks that refer to the formula. It will not be hard to change and save them all, but I would prefer to avoid this.  

Does anybody have any ideas?