How can I run my format keeping code only when a range of cells changes?

I'm looking for a solution to keep my format in some cell areas in column
B:B. The format need to be of two different choices, depending on if you got
an "I" or an "K" in the cell to the left, in A:A column.

It should allow users to copy and paste as they use to do, without ruin the
code. I tried with a code creating format conditioning rules with For
....Step 1 ... Next for all cells, running at Sub Worksheet_Change, but it
shakes like rock and roll every time you make a change.

I just want to make a check in the cell to the left for that specific row
the
change took place, if that is possible. Font black if RC-1 is "K" and blue
if it is "I",

I have tried to start from a macro when recording format conditioning in
excel. A part of it look of cource like this:
...
Selection.FormatConditions.Delete
Selection.FormatConditions.Add Type:=xlExpression, Formula1:= _
"=$A$6:$A$102=""I"""
With Selection.FormatConditions(1).Font
.Bold = True
.Italic = False
.ColorIndex = 1
End With
.... etc

If I want to run code with Sub Worksheet_Change, I guess I had to have a
compleate other approach than "=$A$6:$A$102=""I""" Right?

Because if I let code create the conditional format on every worksheet
changes, it shakes like rock n roll...

Any suggestions??

/My regards