TruClient - Multiply wait time

Hi,

 

We have recently started using truClient, but we have problems when it comes to multiplying wait time (Like the functionality for multiplying think time in http web scripts). The only value we can find is "wait time", but there is no "multiply wait time" setting in runtime settings in Performance Center.

 

We thought about having an external param file and using a value there as base for multiplying think time, but I'm not sure this is very ideal. Is there a "best practice" way to multiply wait-time in truClient scripts ?