Hi Tingyu Du,
I believed this is possible using a Formula base field.
Here's a link where you can check how to create a Formula Field: Datawatch Monarch - Creating a Formula Field
Hope this helps.
There are three approaches - in options, in character list trapping, or in filtering. You can set trapping options to be case sensitive - and then if you know a particular upper case letter will appear in the lines you want, a literal floating trap would work. Or you can use the character list trap feature to set a custom trap character for ABC... - I think this needs v13. Or you can just trap every line and make a filter with the expression field=upper(field).
Hope this helps,
MONARCH ? | ? | ? | ? EXPERTS