In you WritetoField1 sub routine, you need to set the values for the "fields" (thing1 and thing2). Try this:
Sub WriteToField1
Dim obj
Set obj = ThisEvent.Object
If Not obj.Mode = 1 Then
Dim pPageH1, pPageH2
'set a reference to the fields...these need to be the actuall field names in your data (shapefile of .axf)
dim T1, T2
set T1 = ThisEvent.Layer.Forms("EDITFORM").Fields("thing1")
set T2 = ThisEvent.Layer.Forms("EDITFORM").Fields("thing2")
Set pPageH1 = ThisEvent.Layer.Forms("EDITFORM").Pages("pgViewer" )
Set pPageH2 = ThisEvent.Layer.Forms("frmAddNew").Pages("page1")
pPageH1.Controls("listdata").Value = pPageH2.Controls("thing1").Value & ", " & pPageH2.Controls("thing2").value
'set the values of the fields thing1 and thing2
T1.value = pPageH2.Controls("thing1").Value
T2.value = pPageH2.Controls("thing2").value
End If
End Sub
I realize this code looks crude, but it should give you the idea.