Excel hyperlinks: Non drive specific

Wonderful instructions. However, my query is how to create a hyperlink in relation to the folder in which the excel file is situated.

I.e. The excel file is in the folder 'Subject', and the hyperlinked file is located in the folder 'Subject\Image'.

The hyperlinks work fine, but the folders are contained on a USB Stick, so when the USB is transferred to another computer, the links won't always work, as the USB appears as a different drive letter, i.e., 'G:', rather than 'F:'.
How can I create a hyperlink which is related to the folder path (Subject\Image), rather than the whole path (F:\....\Subject\Image)?

I am using Excel 2003, although I believe the instructions would be similar throughout different versions.

Any help would be much appreciated.