In case you are working with different report items (RichTextBox for displaying text and Picture control for dispalying image), then the requested behavior cannot be implemented. This is due to the reason that a report has a static design and a single control cannot have varying width.
A workaround to implement this is to make use of the RTF file that has both text and image aligned in the desired manner. And load this RTF in the RichTextBox control in report.
Regards, Mohita