Currency conversion - Customised program

hi,

We have a customised program where there is currency conversion is required. When I am running the program for a company code it is throughing the error as Currency conversion failed. UoM is different from PO UoM. can anybody please throw some tight on this issue as to what are the changes required and where we need to make the same.

Please let me know where we can make the settings forConversion rates between Local currency and USD.

Thanks in advance.

Regards,

S.Sumana