Add a dimension in Pivot Table based on two fields

[#1]

I would like to add a Dimension in a Pivot Table which is based on two other Dimensions values. Syntax if the following

If([Corporate Account]='OTHER', [Sales Account], [Corporate Account])

If the Corporate Account for the cell is Other, I would like the dimension's value to be Sales Account, and else Corporate Account.

I suspect that [Sales Account] is the name of the field, but does not refer to the value of the field for one very cell. Same with [Corporate Account]. How can I refer to the value of the Dimension [Sales Account] or [Corporate Account] for one very cell in pivot table ?

What is wrong with this syntax ?

Thanks in advance.