Function call Issue

I don’t know if this is obvious, I’m not a PHP programmer. I want to call the function in php and integrate it with my theme. I’m using this function:

<?php echo currencyr_exchange( array( ‘amount’ => 7000, ‘to’ => ‘usd’ ) ); ?>

I want is to be able to use a function for the price instead of a numeric value, like this:

<?php echo currencyr_exchange( array( ‘amount’ => listing_price(), ‘to’ => ‘usd’ ) ); ?>

Can it be done? maybe my syntax is wrong, I know, but there must be a way to call the price function as the value for ‘amount’.

Hope you can help, BTW the theme I’m using is WP pro Real Estate 4.

Regards

http://ww.wp.xz.cn/plugins/currencyr/