calculation don't work ?! [Math Calculations]

Dear sirs,

I have 2 columns with type “price”. The second column is the first one - 13€.
You have any ideas why the following code doesn’t work? Is there any mistake?

[code]
Grid.setColTypes(“link,ro,acheck,ro,ro,ro,ro,ro,ro,ed,ed,ro,ro,ro,ro,price,price[=c15-13],ro”);
[\code]
Thank you in advance.

greetings
Oliver

Does it show any js errors ?
Code looks valid, and if dhtmlxgrid_math.js was included - it must show the valid value.