That would be a pretty nifty feature to have, wouldn't it? Until then, you'll just have to manually adjust and/or set the time for the sheets. It helps if you use this formula:
(Length of each beat in seconds) = 60 / (Tempo)
For example, if you wanted to place a sheet starting 2 measures after the beginning of the song at a tempo of 100 (assuming there is 4 beats in every measure):
60 / 100BPM = 0.6 seconds
4 beats per measure * 2 measures = 8 beats
0.6 seconds * 8 beats = 4.8 seconds for every 2 measures
Therefore, the sheet would be placed at 4.8 seconds.