Problems with populating an expression box, based on another control

[Stumbler]

I' am trying to full in the an article price based on a selected
article name.
I've added an expressionbox with the formula:
xdXDocument:GetDOM("LOCALSALES_ARTICLES")/dfs:myFields/dfs:dataFields/
d:LOCALSALES_ARTICLES/@UnitPrice[@ArticleID = 4], but i can't get any v

 

[Stumbler]

Sorry, I hit the sent key to early

I' am trying to full in the an article price based on a selected
article name.
I've added an expressionbox with the formula:
xdXDocument:GetDOM("LOCALSALES_ARTICLES")/dfs:myFields/dfs:dataFields/
d:LOCALSALES_ARTICLES/@UnitPrice[@ArticleID = 4]

I came up to that solution by reading
http://blogs.msdn.com/infopath/archive/2004/09/13/228881.aspx

If I don't fill in a citerium (leave out [@ArticleID = 4]), I get the
first record, so I think my source is OK.

Can anyone tell me what I am doing wrong

Kind Regards,
Hans (struggling with my first infopath form)

 

[Stumbler]

Sorry, I hit the sent key to early

I' am trying to full in the an article price based on a selected
article name.
I've added an expressionbox with the formula:
xdXDocument:GetDOM("LOCALSALES_ARTICLES")/dfs:myFields/dfs:dataFields/
d:LOCALSALES_ARTICLES/@UnitPrice[@ArticleID = 4]

I came up to that solution by readinghttp://blogs.msdn.com/infopath/archive/2004/09/13/228881.aspx

If I don't fill in a citerium (leave out [@ArticleID = 4]), I get the
first record, so I think my source is OK.

Can anyone tell me what I am doing wrong

Kind Regards,
Hans (struggling with my first infopath form)

I am using Infopath 2003