Setting One Previous Value To Other Field

I have one table in the database with the following fields.
table name: Information
fields:
id type(int)

Rec_From type(varchar)

Send To Dropbox which contains two values Sect1 and Sect2
I want, on updating the record, the previous value of "Send To" field should be assigned to "Rec_From" field. for example the value of "Send To" field is Sect1 and I want to update the field and change the "Send To" as Sect2 and after update the sect1 should be assigned to Rec_From. How should do this.
Thanks in advance