Use 'EXECUTE IMMEDIATE' to execute an update statement : Execute immediate « PL SQL Statements « Oracle PL/SQL Tutorial

SQL>
SQL> CREATE OR REPLACE FUNCTION updnval (
  2     col        IN   VARCHAR2
  3   , val        IN   NUMBER
  4   , start_in   IN   DATE
  5   , end_in     IN   DATE
  6  )
  7     RETURN PLS_INTEGER
  8  IS
  9  BEGIN
 10     EXECUTE IMMEDIATE    'UPDATE employee SET '
 11                       || col
 12                       || ' = :the_value
 13          WHERE hire_date BETWEEN :lo AND :hi'
 14                 USING val, start_in, end_in;
 15
 16     RETURN SQL%ROWCOUNT;
 17  END;
 18  /

Function created.

SQL>
SQL>

22.16.Execute immediate
	22.16.1.	Simple EXECUTE IMMEDIATE
	22.16.2.	Call EXECUTE IMMEDIATE in Pl/SQL block
	22.16.3.	Execute sql statement in a procedure
	22.16.4.	'execute immediate in' action
	22.16.5.	Define a procedure to drop a database object
	22.16.6.	Create a function to count table row
	22.16.7.	Use procedure to create an index dynamically
	22.16.8.	Call function and get result by using 'EXECUTE IMMEDIATE'
	22.16.9.	EXECUTE IMMEDIATE dynamic sql to alter session
	22.16.10.	Use 'execute immediate' to run a insert statement
	22.16.11.	select into rowtype then use it in 'execute immediate'
	22.16.12.	Quotation string
	22.16.13.	Use 'EXECUTE IMMEDIATE' to execute an update statement
	22.16.14.	Wrap 'EXECUTE IMMEDIATE' for current user
	22.16.15.	Wrap statement with 'BEGIN...END'
	22.16.16.	Catch exception from 'EXECUTE IMMEDIATE'
	22.16.17.	EXECUTE IMMEDIATE USING IN
	22.16.18.	Drop user, create user and grant permission with PL/SQL code
	22.16.19.	execute immediate into
	22.16.20.	Update row with 'execute immediate'