Glad you found that useful.
Hope I understand your question...  Let's see, we have
     BSlide.Duration = 2500 - ASlide.RT
and since RT = (ASlide.RTTime - ASlide.OnsetTime), that is the same as
     BSlide.Duration = 2500 - (ASlide.RTTime - ASlide.OnsetTime)
which is not all that different from
     BSlide.Duration = 2500 - (Clock.Read - ASlide.OnsetTime)
So the difference is slight.  But here's the 
deal.  The goal here is to make BSlide end 
precisely 2500 ms after the onset of 
ASlide.  Some small time may pass between 
ASlide.RTTime and the time when BSlide starts, 
and if that happens then if you base 
BSlide.Duration on ASlide.RTTime then the 
Duration will be a little too long and that will 
make the full time of ASlide + BSlide longer than 
intended.  Using the Clock.Read in code 
immediately before BSlide should give you a 
closer estimate of the Duration needed for 
BSlide, but even here, any delay between the 
computation of BSlide.Duration and when BSlide 
actually starts running will result in Duration 
being just a little too long.  May not be enough 
to matter, but why not be more exact if we can?
So I advise *against* doing things this way just 
because of the complications of all these little 
delays.  Instead, my main advice of using 
SetNextTargetOnsetTime along with Cumulative 
timing mode avoids these complications, and used 
properly, can result in precise timing.
At 10/30/2013 11:03 PM Wednesday, =?GB2312?B?vKrP6cjn0uI=?= wrote:
>Dear  David McFarlane,
>  I have tried your suggestion, it really works 
> and it's quite simple compared with what I 
> performed before as : 
> BSlide.Duration=2500-ASlide.RT,  and one more 
> question, why you use 2500 - (Clock.Read - ASlide.OnsetTime).
>Thanks a lot.
>
>
>2013/10/22 David McFarlane <<mailto:
mcfa...@msu.edu>
mcfa...@msu.edu>
><
https://groups.google.com/d/topic/e-prime/dWpfjk-BeLs>
https://groups.google.com/d/topic/e-prime/dWpfjk-BeLs 
>and 
><
https://groups.google.com/d/topic/e-prime/g1Fv2CGaSeg>
https://groups.google.com/d/topic/e-prime/g1Fv2CGaSeg 
>).
>
>Manipulating Duration (instead of 
>NextTargetOnsetTime) also means that the actual 
>duration of BSlide (and ASlide + BSlide) will 
>vary depending on any delays in starting BSlide, 
>but maybe that is what you want.
>
>
>-----
>David McFarlane
>E-Prime training 
>online: 
><
http://psychology.msu.edu/Workshops_Courses/eprime.aspx>
http://psychology.msu.edu/Workshops_Courses/eprime.aspx
>Twitter:  @EPrimeMaster 
>(<
https://twitter.com/EPrimeMaster>
https://twitter.com/EPrimeMaster )
>
>/----
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>/----
>Stock reminder:  1) I do not work for PST.  2) 
>PST's trained staff take any and all questions 
>at 
><
https://support.pstnet.com>
https://support.pstnet.com 
>, and they strive to respond to all requests in 
>24-48 hours, so make full use of it.  3) In 
>addition, PST offers several instructional 
>videos on their YouTube channel 
>(<
http://www.youtube.com/user/PSTNET>
http://www.youtube.com/user/PSTNET