Modifying existing script

How hard is is it to take an existing script and cut out the part you want and add it to a new script that I've written?  For example Brian has a script called Date Creation Database and I want his dialog box (opens a box where you enter a start date and an end date and then buttons for equal to, etc) but I want to add that to a IDEAScript that pulls certain columns from a table (database).  Then apply criteria to dates to show me those invoices who have doc dates less than invoice receipt dates.
End result is I want to be able to find transactions who fail to meet certain criteria related to an audit. I'd like to be able to do this on a monthly or quarterly basis and not have to sort through previous years or months worth of data to get what I'm looking for.