Transfer data in an other text box field on a condition

[Fred's]

Hi folks,

I have a field on my report that show me a sum of "cartons to
received" for each truck appointed.
now I want to transfer that sum of "cartons to received" into another
text box if the cartons are received.

Anyone have an idea, how can I do this? If you need additional
details, let me know.

Thanking you in advance for your support
Fred's