populating stack with field

[Bob Hartley]

Hi All.

I am almost a complete newbie and only made one app for my lab with a lot 
of help from Sarah. I am back in runrev to make a labbook and I'm making a 
testapp to try the concept. So please excuse the stupidity.

I only need to get me head around one thing then I'm off and running. I 
hope you can help.

I have a main stack "mainstack" with buttons on it, one called 
"Addtextfield" . I have 2 other stacks
1)"Textfield" with a card on it called "TextfieldCard" and a field in this 
called "InsertTextfield"
2)"BlankStack" with a card called "BlankCard with nothing on it.

I want the button "Addtextfield" on the "mainstack" to duplicate the field 
"InsertTextfield" and place the copy on on the card "BlankCard" on stack 
"BlankStack"

I am using the script

on mouseUp
   add field "InsertTextfield" to BlankCard
end mouseUp


This seems too simple and indeed it does not work. Am I missing something 
simple or is it a lot more difficult than this. I also have vol1 of dan's 
book but cant see something on first look.

All the best
Bob