Remove part of string

I have a column as such:
123/456
RENT/214
789/456
123/989

What I need to do is, look at the text before the "/" and replace the whole string with another string (based on the pre-defined value).

I have created a loop to loop through the rows in the a single column and replace a specific value:

 Range("b2").Select
     For q = 0 To 10
     If ActiveCell.Offset(q, 0).Value = Left("123/456",7) THEN
 ActiveCell.Offset(q, 0).Value = "555"
 End If
      Next q

I haven't figured out how to strip part of the word. Any help would be appreciated.