Automatically Fill In Column When Certain Cell In Column Changed

I am trying to have some automation to my WS and what I want to do, is if a certain column (column 104) is changed, it will fill out that column with the data entered as long as the account is the same (column 5). Here is the code I tried, but realized very quickly, it puts me into a loop. This is being called by a change worksheet fuction

If Target.Column = 104 Then
If IsEmpty(Target) Then
Else
testacct = Cells(Target.Row, 5)
temptest = testacct
s_TempSwitch = Target.Value
Testoffset = 0
Do While temptest = testacct
temptest = Cells(Target.Row + Testoffset, 5)
Cells(Target.Row + Testoffset, 104).Value = s_TempSwitch
Testoffset = Testoffset + 1
Loop
End If
End If