Line chart not incorporating Negative numbers

[#1]

I have a line chart and I used Field1-Field2 to report the position of the line. Field 1 and 2 are both currency types. Sometimes they will yield a negative number, other times a positive so the line must fluctuate along the x axis accordingly. for some reason, which is driving me CRAZY, negative numbers are being interpeted as positive numbers unless I click on te listbox value for the field, then it displays its negative position. I have no ideo why this isnt working. I cant attach a qvw file but im taking screenshots of everything ive done so far, make you can figure it out

Really need some help with it.The first pic shows a section where the field should be negative but it coming up a completely weird positive number.

***another weird thing, when I make a list box with Sum(field1-field2), it gives a list of currency numbers but the negative currency number are engulfed in perenthesis, not preceded by a negative sign which is expected. I have no idea whats going on. (the field names might not make sense because i renamed  them weirdly. but its supposed to be that, po-listnum

Would really appreciate it

Thanks

[#2]

can you post a small sample file