Return sub-strings between certain characters from a long string (de-concatenate)

Hi, I have a string which goes //John/McCormick/25

The slash is used to divide the string into a few parts. Now I would like to return them, i.e. to de-concatenate and retrieve:

*nothing ("") for the first position,
*"John" for the second position,
*"McCormick" for the third position, and
*"25" for the fourth position.

If I was able to retrieve position of slashes within the string, I could use something like this:
*MID(cell, position of the 1st slash, position of the 2nd slash)
*MID(cell, position of the 2nd slash, position of the 3rd slash)
*MID(cell, position of the 3rd slash, position of the 4th slash)
*MID(cell, position of the 4th slash, position of the 5th slash)