What language do I convert my Avenue scripts to in ArcGIS 10.1 Desktop?

I am moving to ArcGIS 10.1 Desktop Basic from Arcview 3.2a. What language do I use to rewrite all my Avenue scripts? I use custom toolbars and a lot of user selection of objects from views. Below is a typical script that will flip the direction of a line for correct routing of a road centerline:

theView = av.GetActiveDoc
theDisplay = theView.GetDisplay
theTheme = theView.GetActiveThemes.Get(0)
theRectangle = theView.ReturnUserRect

'Select a line
If (theRectangle.IsNull) then
thePoint = theView.GetDisplay.ReturnUserPoint
theTheme.SelectByPoint(thePoint,#VTAB_SELTYPE_NEW)
else
theTheme.SelectByRect(theRectangle,#VTAB_SELTYPE_NEW)
end

theFTab = theTheme.GetFTab
field1 = theFTab.FindField("Shape")

for each rec in theFTab.GetSelection
aline = theFTab.ReturnValue(field1,rec)

'SET THE FLIPPED LINE TO A VARIABLE
newline = aline.flip

'SET THE SHAPE FIELD'S VALUE TO NEWLINE
theFTab.SetValue(field1, rec, newline)
end

theFTab.GetSelection.ClearAll

'INVALIDATE THE VIEW
theView.invalidate
theDisplay.Flush

Thanks in advance for your help!