No, once it's embedded, the link to the external file is broken. You need to reload the original file from scratch and select Link to File.
The Embed and Link to File options are located in the Linkage Status control, in the Photoshop Document Linking section of the Image Texture dialog. They are also available in the Image map dialog, where you load image maps into a texture.
For more information see Chapter 9 - Using Image Textures in the User Guide.