Hi Deepak,
you can run the business rule for currency conversion as part of your default, I do that all the time. Simply add the relevant code directly in your default logic or, if you have it in another script, add a line to default to include that other script.
This is what I usually have in my default:
// FXR business rule
*RUN_PROGRAM CURR_CONVERSION
CATEGORY=%CATEGORY_SET%
CURRENCY=EUR
TID_RA=%TIME_SET%
RATEENTITY=GLOBAL
*ENDRUN_PROGRAM
Since when you send data (and trigger default) you usually do so in LC you need to hardcode the currency rather than have it as %CURRENCY_SET%.
BR,
Arnold