Auto calculate based on column value

[looney]

Hi All,

So I have this code to multiply entries made in J9:L9 by the value in the same column cell 4.

Private Sub Worksheet_Change(ByVal Target As Range)

If Application.Intersect(Target, Range("J9:L38")) Is Nothing Then Exit Sub
If Target.CountLarge <> 1 Then Exit Sub
On Error GoTo catch

Application.EnableEvents = False
Target.Value = Target.Value * Cells(4, Target.Column)

catch:
Application.EnableEvents = True

End Sub

I want to change this so that entires would instead multiply by whatever is in column K, but keeping a relative cell reference, for example:

Enter a value in J9 and the result will be J9*K9
Enter a value in J9 and the result will be J10*K10
Enter a value in J9 and the result will be L9*K9
Enter a value in J9 and the result will be L10*K10

A great bonus to have would be a message box that would run asking the user to fill column K first, if they try to enter a value in the range J9:L38, but K is empty.

Thank you in advance!