InfoPath Dev

I've got one field in my form called INVOICE_AMT.  I'm trying to require a non-zero value in that field.  There are 2 other fields that this is conditioned upon:  INVOICE_DETAIL and DNP.  Here's how it should work.

If INVOICE_DETAIL is equal to CPF, APF, or HRB Simple AND
DNP is equal to False AND
INVOICE_AMT is equal to 0 OR
INVOICE_AMT is blank

Then the INVOICE_AMT field should be required to be more than 0.

No matter what I do, I cannot get this thing to work.  Here's how my condition currently works:

 If this condition is true:

INVOICE_AMT is less than or equal to 0 and
The expression ../@INVOICE_DETAIL = "CPF" or "APF" or "HRB Simple" and
DNP is equal to "False"

It's screwing things all up and giving me the wrong validation.  I've tried this so many times, but I can't get it to work.  I'm in desparate need of some help on this one.

Maybe you need to add parentheses around the terms in your OR expressions to make sure that the entire OR is evaluated as opposed to just the first term. :)

It's the same idea as in albebra - if your formula has multiplication and addition, you need to put parentheses around your plus signs... http://en.wikipedia.org/wiki/Bracket_(mathematics)

Brilliant, but it didn't quite work.  What I figured out is that I needed to use an expression.  It ended up being:

../@INVOICE_DETAIL = "CPF" or ../@INVOICE_DETAIL = "APF" or ../@INVOICE_DETAIL = "HRB Simple"

 That seemed to make it check each variable and treat the whole line as one validation.

Thank you for your solution stormseeker75.  I was having similar problem writing the expression correctly.  Your solution made me realize I needed to use the xpath value in the express (i.e. ../my:fieldname)