Stored Procedure: Copy table from; path = text variable

Hi, in a stored procedure, if I do
COPY table FROM 'mypath' DELIMITERS '\t'; it works but if my path is a text variable which contain my path, i.e.
COPY table FROM mytextvar DELIMITERS '\t'; it doesn't work, I get

ERROR: syntax error at or near "$1"
SQL state: 42601
Context: SQL statement in PL/PgSQL function "parseinsert" near line 15

Is there any workaround? I want to create a temporary table, copy from and parse the table, all with dynamic path depending of how the function is called.

Thank's
Charles