GOOD ADVICE on setting paths to import files from Mike Duncan:
Here is a tip to have your cake and eat it too.
Just for example, let's say we are importing a comma separated value file. Create a copy (perhaps populate with sample data) of the file you want to import and name it something like "Sample_Import_Mapping.csv" and put it somewhere that makes sense - somewhere that you keep project notes or other documentation.
Click the button to select the file to import. After the variable used to reference your file path, click the button to add a file...then select your copy of the file to import with sample data. It will add another line to this dialog...so when the first file reference isn't found, the next listed reference will be found.
Sometimes you have to fool FileMaker into doing what you want in order to make your customer's job easier. This is a good example. Read the whole thing.