Question about increasing Attribute Cost

[geoffnsandiego]

So this is what is my skeleton system:

<!-- Attribute component
Each attribute possessed by the actor derives from this component
-->
<component
id="Attribute"
name="Attribute"
autocompset="no">

<!-- Attributes have a minimum trait value of 1 -->
<eval index="1" phase="Initialize" priority="3000"><![CDATA[
field[trtMinimum].value = 1
]]></eval>

<!-- Each attribute point above one that is allocated by the user costs 7 CP -->
<eval index="2" phase="Traits" priority="10000">
<before name="Calc resLeft"/>
<after name="Bound trtUser"/><![CDATA[
hero.child[resCP].field[resSpent].value += (field[trtUser].value - 1) * 7
]]></eval>

I want Attributes to be based on an increasing scale as follows:

Each point up to 14 costs 15 AP(CP) each
15 costs 30 AP
16 costs 45 AP
17 costs 60 AP
you get the idea

I know it needs to go here:

<after name="Bound trtUser"/><![CDATA[
hero.child[resCP].field[resSpent].value += (field[trtUser].value - 1) * 7
]]></eval>

But I'm not sure how to go about it. Any help would be greatly appreciated.

Geoff