VBA to auto fill or allow data entry

[Sarahj0630]

I feel like this is fairly easy but for some reason (call it pregnancy brain) I can't get it to work. I have this checkbox to automate if the split is 50/50 and it automatically puts in the value into the MaxInvest (E9) and HorizonInvest (I7) fields. I also want to be able to manually enter in values those fields as well, in case the split is not 50/50. If a value is entered in either Investment cells, then it will automatically calculate what the other investment would be left with. I have it working if we change the MaxInvest but it wont work on the Horizon, it is like the formula is overriding itself. Thanks!

Private Sub CheckBox1_Click()


If CheckBox1.Value = True Then ThisWorkbook.Sheets("Barbell Strategy").Range("E9, I7").Value = Range("Fifty")
If CheckBox1.Value = False Then ThisWorkbook.Sheets("Barbell Strategy").Range("E9, I7").ClearContents

End Sub

Private Sub Worksheet_SelectionChange(ByVal Target As Range)


If Range("E9").Value <> Range("Fifty").Value Then Range("I7") = Range("J7").Value
If Range("I7").Value <> Range("Fifty").Value Then Range("E9") = Range("F9").Value

End Sub