Calculate the distance between points in two different themes with a common ID

Procedure

Code:
'--- Calcdist.ave
'--- This script is a modification of the calcdist.ave sample script.
'--- It calculates distances from every selected point in
'--- one point-theme to every point in another point theme.
'--- It will only calculate distances between points that have a common ID value. 

theThemeList = av.GetActiveDoc.GetThemes.Clone
newThemeList = {}

for each thm in theThemeList
  if (thm.getftab.findfield("shape").gettype = #FIELD_ShapePOINT) then
    newThemeList.add(thm)
  end
end   

thePrj = av.GetActiveDoc.GetProjection

'--- Use these lines to prompt the user for input parameters...

theFromTheme = (MsgBox.List (newThemeList,"to calculate the distance FROM.", "Please select a point theme..."))

if (theFromTheme = nil) then exit end 
theFromFtab = theFromTheme.GetFTab
newThemeList.RemoveObj(theFromTheme) 
  
theToTheme = (MsgBox.List(newThemeList,"to calculate the distance TO.", "Please select a point theme..."))

if (theToTheme = nil) then exit end  
theToFtab = theToTheme.GetFTab

theFromIDField = MsgBox.ListAsString(theFromFtab.GetFields, "containing the point identifier.","From Theme: Please select a field...")

  if (theFromIDField = nil) then
    exit
  end 
theToIDField = MsgBox.ListAsString(theToFtab.GetFields,"containing the point
identifier.", "To Theme: Please select a field...")
  if (theToIDField = nil) then
    exit
  end     

theFromShapeField = theFromFTab.FindField("Shape")            
theToShapeField = theToFtab.FindField("Shape")

theToFtab.SetEditable(true)

theNewFieldName = msgbox.input
'--- If the field name already exists in the table,
'--- its values will get overwritten",
"Input a field name for your new distance field:","dist_2_id(x)")
  
'--- If a distance field doesn't exist, add it...
if (theToFtab.FindField(theNewFieldName) = nil) then
  
'--- Choose the field size commensurate with the view's projection.
  if (thePrj.IsNull) then
    theDistanceField = field.make(theNewFieldName,#field_decimal,8,4)
  else
    theDistanceField = field.make(theNewFieldName,#field_decimal,8,2)
  end
      
    theToFtab.addfields({theDistanceField})
'--- If a distance field does exist, clear it...    
else
  if (theToFtab.FindField(theNewFieldName).IsTypeString = true) then
    MsgBox.Info("Your input field name cannot be overwritten with number
values", "Please start over and select a different field name...")
    exit
  end  
  theToFtab.Calculate("0",theToFtab.FindField(theNewFieldName))
  theDistanceField = theToFTab.FindField(theNewFieldName)  
end 

if (theFromFtab.GetSelection.Count = 0) then
  theRecordsToCalc = theFromFtab
  numRecs = theFromFtab.GetNumRecords
else
  theRecordsToCalc = theFromFtab.GetSelection
  numRecs = theRecordsToCalc.Count
end

for each f in theRecordsToCalc
  av.ShowMsg("Calculating Distance Values")
  av.SetStatus( (f / numRecs) * 100 )
'--- Get the point location you are measuring FROM. 
'--- If the view is projected, get the point location in projected units.
  theID = theFromFtab.ReturnValue(theFromIDField,f)
  theFromShape = theFromFTab.ReturnValue(theFromShapeField,f)
  if (thePrj.IsNull.Not) then
    theFromShape = theFromShape.ReturnProjected(thePrj)
  end  
  
  for each t in theToFtab
    theToID = theToFtab.returnvalue(thetoidfield,t)
    'msgbox.info("thetoid",thetoid.asstring)
      if (thetoid = theid) then
        '  Get the point location you are measuring TO.
        '  Get it in projected units, if the view is projected.
        theToShape = theToFTab.ReturnValue(theToFtab.FindField("Shape"),t)
          if (thePrj.IsNull.Not) then
            theToShape = theToShape.ReturnProjected(thePrj)
          end

'--- Calculate the distance between the two points.
'--- Add the value to the output (TO) branch table.    
        theDistance = theFromShape.Distance(theToShape)
        theToFtab.SetValue(theDistanceField,t,theDistance)
      end
  end
  
end  

av.ClearMsg
av.ClearStatus 

theToFtab.SetEditable(false)

av.ShowMsg("Distance calculation complete") 

'--- End of Script

Note:
This script can be downloaded from the ArcScripts page:
http://arcscripts.esri.com/