how to compare nth row value of one dataset with fist row value of other

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HI i had a requirement where i need to compare two values and change the color of the marker ,one dataset has like 15 rows and other has 1 row , what i need to do is compare the value of 1 row dataset with other dataset and have to change it , the expression i am using now is like this

iif(Fields!Time.Value=First(Fields!chart_endtime.Value, "dset_lowcosttrade"),"Black","#00ffffff")

but i am having problem here it is only taking the first row value, but my value will be some wehre in th nth row , so is there any way i can compare the endtime value(single row datasetvalue) with time (dataset with 15 rows), is there nay way to acieve it ,please let me know thanks in advance