What is the syntax to change the current directory?

ChDir (<directory path>)

'examples - changes current directory to Desktop folder
ChDir "C:\UserA\Desktop"

 

 

What is the syntax to run code every time a cell value changes?

'place code in a sheet under Microsoft Excel Objects
Private Sub Worksheet_Change(ByVal Target As Range)
     If target.Row = Range("<range of cell>").Row And target.Column = Range("<range of cells>").Column Then
        <code to be run here>
     End If
End Sub

'example
Private Sub Worksheet_Change(ByVal Target As Range)
     If target.Row = Range("A1").Row And target.Column = Range("A1").Column Then
        MsgBox("The value of A1 has changed")
     End If
End Sub