comparing current value with previous value in cell of excel sheet linked to rtd

i have excel sheet linked to real time data(stock ticks), i want to compare value of current tick to that of previous tick in given cell (is new value greater than or lesser than previous)e.g. stock price ticks- i want to compare price in current tick to that of previous value so that i can know was it increment or decrease,i can do this by transferring data to .csv file and then processing it but i like to know is there any method so that i can do this in excel itself using excel formulas or vba etc.?i have excel 2010 version
regards

You could use the Calculate event and a Static variable

Private Sub Worksheet_Calculate()
    Static vPrior As Variant
    With Range("A1")
        If .Value <> vPrior Then
            MsgBox "New: " & .Value & vbLf & vbLf & "Old: " & vPrior, vbInformation, "Change"
            vPrior = .Value
        End If
    End With
End Sub

How practical the above approach will be for you will depend largely on frequency of update etc... use of MsgBox purely for sake of demo.

Also, if you're comparing a lot of values simultaneously I would suggest you cache the prior values rather than a multitude of Static variables.
(note: Static variables only persist within session)

thanks donkeyote, and yes, i am comparing 50 values at a time,so i guess i have to cache data, is there way to cache it temporarily within excel, i mean save just previous value for comparison,and delete it on next input ,i searched but can't find anything about it