Easiest would be to access the buffer(s) in the browse, not the browse itself.
If you have a browse showing the table "Customer" you can put something like this in the "VALUE-CHANGED" trigger:
DEFINE VARIABLE c-value AS CHARACTER NO-UNDO.
IF AVAILABLE customer THEN DO:
c-value = customer.custName.
MESSAGE c-value
VIEW-AS ALERT-BOX INFORMATION.
END.
For a browse with MULTIPLE-SELECTION enabled you would have to do something like this (works for a single selection browse as well - NUM-SELECTED-ROWS will never be more than one in that case):
DEFINE VARIABLE i AS INTEGER NO-UNDO.
DEFINE VARIABLE c-value AS CHARACTER NO-UNDO.
/* The browse is named brTest */
DO i = 1 TO brTest:NUM-SELECTED-ROWS:
brTest:FETCH-SELECTED-ROW(i).
IF AVAILABLE customer THEN
c-value = c-value + customer.custName + "~n".
END.
MESSAGE c-value VIEW-AS ALERT-BOX.