jasotastic81, thanks for your response. I haven't been able to get that code to work. I'm using LCD ES2 and opening the resulting PDF in Acrobat X. The Add User button has no effect.

I have the Remove User button initially set to Hidden.
In the Add Users button, I added your script, but had to tweak the name a little bit to match my object hierarchy. I also reversed the order of the two lines, figuring the Remove User button has to be made visible before the row gets copied -- does that make sense?
xfa.resolveNode("Page1.UsersRequiringAccess.Table1.RowUserName["+0+"].RemoveUser").presence = "visible"; // Set the button to visible before copying the row
Page1.UsersRequiringAccess.Table1.RowUserName.instanceManager.addInstance();
In the Remove User button, I added:
xfa.resolveNode("Page1.UsersRequiringAccess.Table1.RowUserName["+0+"].RemoveUser").presence = "visible";
Page1.UsersRequiringAccess.Table1.RowUserName.instanceManager.addInstance();
In the form layout:ready event I added
if(Page1.UsersRequiringAccess.Table1.RowUserName.instanceManager.count == 1) xfa.resolveNode("Page1.UsersRequiringAccess.Table1.RowUserName["+0+"].RemoveUser").presence = "hidden";
else xfa.resolveNode("Page1.UsersRequiringAccess.Table1.RowUserName["+0+"].RemoveUser").presence = "visible";
This also brings me to a couple of questions: What's the difference b/w having "()" or "(1)" at the end of "addInstance". When I type in the script and use the automatic pop-up text, it adds "([b1])" at the end.
Also, what is the purpose of "["+0+"]" in your script?
Thanks again for your help.