EL Question - Missing Data Condition

["ndtrader" <ndtrader@xxxxxxxxxxx>]

How do you detect missing data, with an IF statement ?
Let's say we have Data1 and Data2.
Data1 has data on every bar (so that the following code executes on every
bar).
I want to detect those bars on which Data2 is missing:

If ("Data2 is missing on this bar") Then Begin

    End:

How do I write "Data2 is missing on this bar"?

Setting Close of Data2=0 as the condition does not work, it does not get
triggered by missing data.

Thanks in advance.