Add value to the last empty cell in a defined dynamic column - database

Question

My model takes two numbers from one sheet, adds the average to another sheet in the last cell of a defined column. The problem that I have is that when I insert a new column, the references get missed up and I'm trying to have a macro that would 1. take the average 2. look for a specific column on the second sheet 3. paste the averaged value to the last cell.
Please help me with this I have been trying to get my head around it for a long time.
my problem is that I have to insert new columns and I need to keep the references dynamic when adding a value to the last empty cell in a column. For example: if i have salary as col A, and expenses as Col B - in this model that I have now I put in .Cells(emptyRow, 1) and .Cells(emptyRow, 2) now if I insert a column between A and B the references 1 and 2 will not work. Is there anyway that I can work around this where if i add a new column it wont mess up the references in the macro?
Thank you.
This is the code that I have right now but it does not really work - when I insert a new column the column defined name does not shift right.
Sub demo()
Dim expCol As Long, FirstEmptyRow As Long
Range("B:B").Cells.Name = "expenses"
expCol = Range("expenses").Column
FirstEmptyRow = Cells(Rows.Count, expCol).End(xlUp).Row + 1
Cells(FirstEmptyRow, expCol).Value = 123
End Sub
P.S. 123 here is just an example for testing purposes. The value that would replace it in my model is the average I talk about in the question.

Answer 1

If your columns have headers (I guess they do), and your data has no gaps just use
Range("1:1").Find(columnName).End(xlDown).Offset(1,0) = 123
If a column can have just a header but no values, you need to add additional check if second row isn't empty.

Answer 2

If you create a named range this way (rather than the Range.Cells.Name way you were using), then when inserting columns the reference will be dynamic. Now if you insert columns between A and B later in the code, you can still use expCol and FirstEmptyRow to reference the first empty cell in the expenses column, where ever it may have moved to on the sheet, as long as you update them after each column insertion.
Sub Demo()
Dim expensesrng As Range
Dim Expenses As Range
Dim expCol As Long
Dim Exprng As Range
Dim FirstEmptyRow As Long
'set the original range to use for the expense column
Set expensesrng = Range(Range("B1"), Range("B1").End(xlDown))
'add the named range
ActiveWorkbook.Names.Add Name:="Expenses", RefersTo:=expensesrng
' create a variable to refer to the Expenses Range
Set Exprng = ActiveWorkbook.Names("Expenses").RefersToRange
expCol = ActiveWorkbook.Names("Expenses").RefersToRange.Column
FirstEmptyRow = Exprng.End(xlDown).Offset(1, 0).Row
Cells(FirstEmptyRow, expCol).Value = 123
'after inserting columns then you will have to get/update the column number
'of the expense named range and the first empty row before adding your new expense
'data to it
Range("B:B").Insert Shift:=xlShiftToRight
expCol = ActiveWorkbook.Names("Expenses").RefersToRange.Column
FirstEmptyRow = expensesrng.End(xlDown).Offset(1, 0).Row
Cells(FirstEmptyRow, expCol).Value = 123
End Sub