Function Code To Log Field Changes Into A Table?

As you can see the purpose of this function code is to register into the TblLogChanges every single record exclusion or record change made in any form field of my project when the form is active. In other words if the user changes for example the value of the field Color in the form FrmX from Yellow to Black, the TblLogChanges will have added a line indicating: FrmX, type of change (record change or record exclusion), RecordId (in my case CADID), Current User, Date, and a complimentary string showing Field Color old value=Yellow --> Field Color new value=Black.It works fine when the field "old" value is populated (not null). However, if the feld old value is null, meaning, if the field value is originally null, or yet if the field is originally empty, and I fill it up with some data, then the code does not add an indicative line into the table TblLogChanges.

See function code below.

FYI the function is called in both Before Update and Delete events of the form with the following syntaxes: =logChangeFrmCadastro("E") for record exclusions, and =logChangeFrmCadastro("A") for record changes.

I have failed so far to make it happen. Reason is I'm able to read and understand most written syntax but still not good enough to create my own codes since I do not know to use the range of VBA commands and syntaxes available yet. This is a knowledge gap I'm doing my best to fill in.

what function code changes are required so the function be able to add an indicative line into TblLogChanges when the user changes a form field from "empty/nothing" to something?

Code:
Option Compare Database
Option Explicit
Function LogChangeFrmCadastro(strTipo As String)
On Error Resume Next
Dim db As Database, rslog As Recordset
Dim frm As Form, I As Integer

[code]....