Excel add-in to import csv as text fields

I want to create an Excel add-in that does the following: If the file being opened (Workbook_Open event) is .csv and column values are in quotes, then import columns as text field type. Excel annoyingly tries to reinterpret fields and determine their type on open, which means zip code fields are interpreted as numbers and lose leading zeroes, etc. If installed, this add-in should automatically open .csv file fields as text type unless the values are not wrapped in quotes (text qualifier). The add-in should also not impede the manual data import functionality in any way (in other words -- people could still walk through the data import and select field types manually -- this add-in only impacts the default behavior for csv files).