VBA Excel find and replace WITHOUT replacing items already replaced - vba

Question

I am looking to make an excel script that can find and replace data, but for the love of everything I cannot figure out how to write it.
Situation:
A-----------B-----------C
Cat-------Dog------Banana
Dog------Fish------Apple
Fish------Cat-------Orange
So the macro would look at the data in a cell in column B, then look at the adjacent cell in column C, and replace all instances of that data in column A with what if found in C. So the results would be:
A---------------B-----------C
Orange------Dog------Banana
Banana------Fish------Apple
Apple--------Cat-------Orange
But that's not all, I would like it to not change cells in A that already have been changed once! (I'm trying this with changing the background colour)
Any help? I am at a complete loss.
EDIT:
Okay I found out how to do the easy part (replacing), but I cannot find out how to not change cells that already have been changed once. Here is my code:
Sub multiFindNReplace()
Dim myList, myRange
Set myList = Sheets("sheet1").Range("A2:B3") 'two column range where find/replace pairs are
Set myRange = Sheets("sheet1").Range("D2:D5") 'range to be searched
For Each cel In myList.Columns(1).Cells
myRange.Replace what:=cel.Value, replacement:=cel.Offset(0, 1).Value, ReplaceFormat:=True
Next cel
End Sub
As far as I can tell, ReplaceFormat:=True
doesn't do anything ;/ so items that already have been replaced once still are being replaced! Is there a way to somehow make this work?

Answer 1

Here's the answer using your recommendation with color as a one-time limiter:
Sub Replace_Once()
'Find last row using last cell in Column B
LastRow = Range("B" & Rows.Count).End(xlUp).Row
'Clear colors in Column A
Range("A1:A" & LastRow).Interior.ColorIndex = xlNone
'Look at each cell in Column B one at a time (Cel is a variable)
For Each Cel In Range("B1:B" & LastRow)
'Compare the cell in Column B with the Value in Column A one at a time (C is a variable)
For Each C In Range("A1:A" & LastRow)
'Check if the Cell in Column A matches the Cell in Column B and sees if the color has changed.
If C.Value = Cel.Value And C.Interior.Color <> RGB(200, 200, 200) Then
'Colors the cell
C.Interior.Color = RGB(200, 200, 200)
'Updates the value in Column A with the cell to the right of the Cell in Column B
C.Value = Cel.Offset(0, 1).Value
End If
Next
Next
'Uncomment the line below to remove color again
'Range("A1:A" & LastRow).Interior.ColorIndex = xlNone
End Sub