ODBC pass a calculated timestamp to DB cause error

in VC++, I need to update a timestamp field with a C++ timestamp(the
seconds
after 19700101), my SQL is like
UPDATE my_table SET time_field=timestamp '1970-01-01
00:00:00'+interval '1 seconds' * ?
OR
UPDATE my_table SET time_field=timestamp '1970-01-01
00:00:00'+interval '? seconds'

then pass in the timestamp as integer parameter,
both works when I use constant instead of parameter, but the parameter
is not
working, how can I pass the timestamp in then?