How to Trying to run code when cell value changes from empty to entered value

How to run code when cell value changes from empty to entered value

Requirement:

The user has a cell range B3:B327 that is initially entered by user & several other cells are activated by the entry. The user is trying to run a code when cell values change from empty to entered values.

Solution:

Code:

 Option Explicit
Private Sub Worksheet_Change(ByVal Target As Range)
'Instructs the user to copy the Social Security number after entering the name.
 If Target.Count > 1 Then Exit Sub
If Intersect(Target, Range("c3:c327")) Is Nothing Then Exit Sub
Dim OldVal As Variant, NewVal As Variant
  Application.EnableEvents = False
    NewVal = Target.Value
    Application.Undo
    OldVal = Target.Value
    ' Test Cell's Previous State
    If IsEmpty(OldVal) Then
    Application.Speech.Speak "Copy the  Social Security Number directly from C.   P.   R.   S.    The system stips  the first five numbers.  ", SpeakAsync:=True
      MsgBox " Copy the Social Security Number directly from CPRS. The system strips the first five numbers.  ", vbInformation, "Vocational Services Database - " & ActiveSheet.Name
    Else
   
    Application.Speech.Speak " You just erased the entry that was there.   Is that what you wanted to do?", SpeakAsync:=True
      MsgBox " You just erased the entry that was there.   Is that what you wanted to do?"
    End If
    ' Accept New Value
      Target.Value = NewVal
  Application.EnableEvents = True
End Sub

Obtained from the OzGrid Help Forum.

Solution provided by FrankM.