Struggling with changing Active Cell Value

Here is the situation:

I am working on project server and let's say one of the requirement is Project managers who access the project through project professional pro on desktop or through the schedule web part in project web app can only do the following

1.) They can only change the % completed column. nothing else can be changed

I do realize there is no disabling columns etc in project so, I am going down the path of writing a MACRO and my logic is

• Let's say a user changes a column other than % completed, then to change the active cells value to the old value

I can find the new value because i am using the App_ProjectBeforeTaskChange sub routine and NewVal i have

I can find the old value by doing ActiveCell.Text

but how do i set the active cell value back to let's say "Hello", i have tried this. here if they change the task name i want to set it to say hello..but it never does, the other values i am able to..

Any help ???

Private Sub App_ProjectBeforeTaskChange(ByVal tsk As Task, ByVal Field As PjField, ByVal NewVal As Variant, Cancel As Boolean)
    
    Dim originalTask As Task
    Set originalTask = ActiveCell.Task
    Dim row As String
    
    If (Field = pjTaskName) Then
        'ActiveCell.Task.SetField FieldID:=pjTaskName, Value:="Hello"
        
    End If
    
End Sub