Email Automation

I am trying to create a document that automatically sends an email whenever a field reaches a certain value. I am pulling the data from different worksheets onto a summary worksheet and using the data on the summary sheet as the point at which my code checks to see whether the value is below the minimum required. The summary sheet updates automatically whenever I change the data in one of the other sheets but the email will not send automatically when the summary sheet is updated. When I run the macro individually the email sends, however I need some way of triggering it so that it sends automatically upon the data in the field changing. Can anyone help me with this?

Here is an example of some of the code I am using:



Private Sub Worksheet_Change(ByVal Target As Range)
If Not Application.Intersect(Range("D3"), Target) Is Nothing Then
If IsNumeric(Target.Value) And Target.Value < 1 Then
ANDES1
End If
End If
If Not Application.Intersect(Range("E3"), Target) Is Nothing Then
If IsNumeric(Target.Value) And Target.Value < 1 Then
ANDES2
End If
End If
End Sub