After the import into Access, I would modify the table by adding two new text type fields.
First new field would be named "NoDashes" and the second new field would be named "NewFormat".
The reason for the two new fields is to 1) keep the original data and 2) watch the progress.....
Run an update query to remove the dashes from the original data field - update the "NoDashes" field. Use the Replace function
Code:
Replace(OrigField, "-","")
Then run an update query to update the "NewFormat" field using the "NoDashes" field. The query would have a column something like
Code:
Left(NoDashes,4) & "-" & Mid(NoDashes,5,3) & "-" & right(NoDashes,3)