Configure one remote key to enable/disable flirc inputs -> This key would set a flag to 0 or 1.
if (flag = 0) and (IR_KEY is "remote key to enable/disable") Set Flag to 1
else if (flag = 1) and (IR_KEY is "remote key to enable/disable") Set Flag to 0
else if flag = 1 then all IR keys accepted
else do nothing;
Easy, don't you think? :P