I did a quick test with an xla and an xls that called a function in the xla.
I converted the xla to an xlam. The formulas that called the function linked
to the old file.
All you would need to change is the path to the original add-in. Install the
new add-in, open the file. You will see #NAME? errors wherever the cell
references the old add-in. do a search and replace, changing the old path to
nothing. For example, my old function was
='C:\Documents and Settings\Jon Peltier\Desktop\Hello\Hello.xla'!Hello()
I need to change this to
=Hello()
It's inconvenient, but it can be automated. For one project I wrote a
routine that detected when a file was opened, then is searched for and
deleted the old path. There was a small lag on file open, which may be
exaggerated in Excel 2007.
- Jon