Selectively resetting fields

I'm having trouble using 'resetData'. Maybe I'm using the wrong thing. I've set up a button to selectively reset my dropdown field within one category [which is TechSF.TACDrop], but it's resetting all the equivalent dropdowns in all categories.

This is my code:
----- form1.TACPg1.TechSF.ResetListBtn::mouseUp: - (JavaScript, client) ----------------------------

if(xfa.host.messageBox("This will clear the current list and your details field, and redisplay the dropdown box. Are you sure?", "Reset List?",2,3) == 4)
{

TechSF.TACResults.clearItems();
TechSF.TACResults.presence = "hidden";
TechSF.TACDtls.presence = "hidden";
TechSF.ResetListBtn.presence = "hidden";
TechSF.TACDrop.presence = "visible"
xfa.host.resetData("xfa.form1.TACPg1.TechSF.TACDrop");

}

As you can see this is also designed to clear a field and hide and redisplay other fields.

I did a search here on 'resetData' and found a reply to a similar query from ThomP in which he uses this code:

xfa.host.resetData("xfa.form.form1.TextField1,xfa.form.form1.TextField2");

I also found the above example in 'LiveCycle Help'. Because this is standalone and not in context, I don't understand the two references contained within the brackets & separated by commas. Seeing as my code isn't working, I assume this is important.

So can someone explain to me why there are 2 references within the brackets and what they mean?
Thanks in advance,
Peta