ChnEventFind could not find timestamp

I have a timestamp channel as

oGrp.Channels("CorrectedDateTime")

I would like to find index where the timestamp is larger than "06/01/2017" and remove data of all channels at index before this timestamps I can successfully use ChnFind to and DataBlDel to do it as:

index = ChnFind("ValEqualGT(A,B)", 1, array("A", "B"), array(oGrp.Channels("CorrectedDateTime"), CDate("06/01/2017")))
Call DataBlDel(oGrp.Channels,1,index-1)

However, it takes long for ChnFind function to find the index.

Is it possible to use ChnEventFind to achieve same result? Here is what I tried but the ChnEventDuration gave 0.

ChnEventResultList = ChnEventFind("(A > B)", array("A","B"),array(Data.GetChannel("[1]/CorrectedDateTime"), CDate("06/01/2017")))
msgbox(ChnEventDuration(ChnEventResultList))

Also, in ChnEventFind, why did it fail when I use oGrp.Channels("CorrectedDateTime") instead of Data.GetChannel("[1]/CorrectedDateTime") ?

Thanks