Hi Vince,
in your case you should add Null points for the missing data. The support for Null points in TFastLine Series has been included in the TeeChart Pro v6. You can find one example in the TeeChart Pro v6 Demo Features project under :
Welcome ! -> New Features -> Series -< Fast Line -> Nulls and Stairs.
If you're using the TeeChart Pro v5 a workaround is to use TLineSeries instead of TFastLineSeries.
Josep Lluis Jorge
http://support.steema.com