I would use two helper columns. Assuming your numbers are in Column A
(starting in Row 2), and assuming you use Column P and Column Q as your
helper columns, put these formulas in the indicated cells and copy down to
the end of your data in Column a and then sort all your data referencing
Columns P and Q as the sorting columns...
P2: =LOOKUP(9.9E+307,--LEFT(A2,ROW($1:$99)))
Q2: =MID(A1,TRIM(RIGHT(SUBSTITUTE(RIGHT(P2),"/",REPT(" ",99)),99))+1,99)
Note: Notice that the formula in Column Q refers to values in Column P.