'GENERATES DX AND DY DISTANCES (E.G. FOR STATE-SPACE ANALYSIS) FROM EARLIER OCCUPIED POINT
'REQUIRES: A POINT SHAPEFILE WITH FILLED-IN X,Y,LOCATIONS AND BLANK DX and DY FIELDS

'LOADING SCRIPTS
' 1. Double-click on an empty area on the bar containing all buttons, The "Customize" dialog appears
' 2. In the "Type" pull-down, select "View"
' 3. In the "Category" pull-down, select "Buttons", The display right below the pull down changes to show an array of buttons
' 4. Slide the scrollbar (below the button display) to the right and select the last button by clicking on it, Now click on "New"
' 5. A new blank button appears. Double-click on the blank area to the right of the entry "Click" (just below the button display)
' 6. The "Script Manager" Dialog appears, Click on "New", Enter any name in the input box that appears (prefix it with "Z_" so that it goes in the last)
' 7. A new blank script document (With the name just specified) appears. Delete whatever is on it...
' 8. Either copy-paste this ENTIRE script on the document, or, click on the button with the open-folder icon (tooltip reads "Load text file") and navigate to this file
' 9. Either done, click on the button with the tick-mark icon ("compile"). If spatial analyst is not loaded, there will be some error message, Load it
' 10. After the script is compiled (the tick-mark buton should be grayed out), close the script window and return to the view
' 11. Click on the new button to run the script

theTable = av.GetActiveDoc
TheVtab=TheTable.GetVtab

LatFld=TheVtab.FindField("Y")
LonFld=TheVtab.FindField("X")
DxtFld=TheVtab.FindField("dx")
DytFld=TheVtab.FindField("dy")

TheVtab.SetEditable(TRUE)

for each rec in TheVtab
  if (rec<>0) then
    LatVal1=TheVtab.ReturnValue(LatFld,rec-1)
    LonVal1=TheVtab.ReturnValue(LonFld,rec-1)

    LatVal2=TheVtab.ReturnValue(LatFld,rec)
    LonVal2=TheVtab.ReturnValue(LonFld,rec)

    Diffx=LonVal2-LonVal1
    Diffy=LatVal2-LatVal1

    DxtVal=TheVtab.SetValue(Dxtfld,rec,Diffx)
    DytVal=TheVtab.SetValue(DytFld,rec,Diffy)
  end
end