You can use the following built-in functions with drop-down list objects.
Function  | 
Description  | 
bottom [of]  | 
Returns the line number of the last line in the drop-down list.  | 
top [of]  | 
Returns the line number of the first line in the drop-down list (which is always 1).  | 
textual line from  | 
Returns the text that appears on the specified line of the drop-down list. (See textual Object Inquiry Built-in Function in the Reference Guide.)  | 
selected line from  | 
Returns the line number of the line that the user has selected from the drop-down list.  | 
window yposition of  | 
Returns the line number of the first line displayed in the drop-down list.  |