HELP Needed urgently

[Badrul]

FactTable:

[TABLE="width: 500"]
<tbody>[TR]
[TD]accountName[/TD]
[TD]amount[/TD]
[/TR]
[TR]
[TD]AAA[/TD]
[TD]100[/TD]
[/TR]
[TR]
[TD]BBB[/TD]
[TD]200[/TD]
[/TR]
</tbody>[/TABLE]

DimFSLineItem
[TABLE="width: 500"]
<tbody>[TR]
[TD]FSLineItem[/TD]
[TD]Level2[/TD]
[TD]Level3[/TD]
[TD]Sign[/TD]
[/TR]
[TR]
[TD]Net parent invesment[/TD]
[TD]SubCategory 1[/TD]
[TD]Category1[/TD]
[TD]1[/TD]
[/TR]
[TR]
[TD]Other equity[/TD]
[TD]SubCategory 1[/TD]
[TD]Category1[/TD]
[TD]-1[/TD]
[/TR]
</tbody>[/TABLE]

DimRollup
[TABLE="width: 500"]
<tbody>[TR]
[TD]accountName[/TD]
[TD]FSLineItem[/TD]
[/TR]
[TR]
[TD]AAA[/TD]
[TD]Net parent investment[/TD]
[/TR]
[TR]
[TD]BBB[/TD]
[TD]Other equity[/TD]
[/TR]
</tbody>[/TABLE]


Question:

I currently use the rollup table to give me a hierarchicaly drill dow report which goes from Category1 down to Sub Category 1 and then the two accounts.
At all these level I want the subtotal to be a sum of account x the sign for the relevant account.

At the moment all my formulas are applying the same sign across everything (I was using the max function). So for Total Category 1 for example, the total shown is AAA amount * 1 + BBB Amount * 1

How am I supposed to handle this?