I'm fairly new to VBA and apologise if this sounds completely stupid.

I've got a userform that users can enter data which then feeds into two worksheets. wks1 has unique information whilst wks2 can have multiple entries. wks1 and wks2 are linked via a unique ID.

Now I need to add a search and an edit function to the userform which is causing a real issue. I've downloaded Roy Cox's amazing database form http://excel-it.com/vba_examples.htm and trying to implement it but I can't seem to get it to work.
The userform is called from another worksheet (let's call it wksIntro for the sake of argument). Where can I specific which worksheet to use? How can I fill the first part of the form using wks1 and second part of the form using wks2 based on the selection from the listbox?

Many thanks in advance!