Millisecond Forums

Hello,
I am very new to Inquisit so this might be a stupid question.  Hope you can help!
I am preparing a task (similar to the TheThe Hungry Monkey).  I want to have 4 practice trials where they answer the training question before the participants can move on to the training game against the computer. 
Each of my training questions is an image.  At the moment I have this:

<trial practice_1>
/ stimulusframes=[1=practice_picture_1]
/ inputdevice=keyboard
/ validresponse = ("0","1","2","3","4")
/ correctresponse = ("3")
/ recorddata = false
/ ontrialend = [ values.correct_practice += trial.practice_1.correct]
</trial>

However, this only shows the image (with the question on it) and no matter how I tried to respond, it doesn't move on.  So I thought I should create a textbox to have a place to collect the response, thus this:

<textbox practice_response>
/ caption = "Your answer:"
/ validresponse = ("0","1","2","3","4")
/ correctresponse = ("3")
/ fontstyle = ("Arial", 4.08%, true, false, false, false, 5, 0)
/ position = (50% , 90%)
/ range = (0, 10)
/ responsefontstyle = ("Arial", 4.08%, true, false, false, false, 5, 0)
/ textboxsize = (30%, 10%)
/ txcolor = black
</textbox>

<trial practice_1>
/ stimulusframes=[1=practice_picture_1, practice_response]
/ inputdevice=keyboard
/ validresponse = ("0","1","2","3","4")
/ correctresponse = ("3")
/ recorddata = false
/ ontrialend = [ values.correct_practice += trial.practice_1.correct]
</trial>

This returns an error that says:  Could not locate element "practice_response".

Can you tell me what is it that I need to change here for it to work?  Thank you in advance!

Thao