You'll need to reformat the path to fit what a store by reference container in filemaker expects.
If your path starts with the C drive and ends with the name of the file, all you need to do is insert imagewin: at the beginning of the path.
Here's an example from one of my DB's:
imagewin:/C:/Documents and Settings/Phil/My Documents/My Pictures/PolyButton.JPG
You can manipulate your container field just as though they are text fields for this so you can use a replace field contents (by calculation) operation to insert the additional text into the beginning of each container field.
Perfect! Thank you.