Sorry for the late reply.
The is no pre-defined macro method for this. You can either create a custom macro for this and use the API to access the controls collection, find the repeater and access its dataset to get the value you need. (custom macros).
You could use K# - but in this case the K# macro will basically be the same as the API code in a custom macro - you would use the same methods and the macro would be pretty complex and hard to read and debug in case of problems.