Once you move several columns, other columns will also change their position. Use TableColumnSubscription to find the position of the column as it is displayed.
With Columns - COL_name, COL_number, COL_size
Move COL_size - TableMoveColumn(MyTable, "COL_size", 1)
Where is COL_number?
TableEnumColumn(MyTable, 3) will return "COL_size"
TableColumnSubscript(MyTable,"COL_number",tcpDisplay) returns 3