If I programmatically change ColumnOrders, I can pull the proper index by:

lnColumn = This.Columns[This.ActiveColumn].ColumnOrder
This.Columns[lnColumn]


My message is not clear ?

If you have 3 columns CL1,CL2,CL3

Start
CL1.ColumnOrder = 1
CL2.ColumnOrder = 2
CL3.ColumnOrder = 3
programmatically change 
CL1.ColumnOrder=3
you have this result
CL1.ColumnOrder = 3
CL2.ColumnOrder = 2
CL3.ColumnOrder = 1
NOW, if
This.ActiveColumn is 3 the active column is CL1
but
This.Columns[This.ActiveColumn] is CL3

If you change the ColumnOrder value,
the expression This.Columns[This.ActiveColumn] it do not have meant.