Dynamic function expression for time field

Hi,

Am working on report builder 3.0 to create a report. And i want to provide dynamic expression to get difference between 2 time values. Below is the detail about the requirement and query am facing at this moment

Have 2 fields in dataset which holds only time(hh:mm:ss format) values. I want to use these fields and get difference in time converted into minutes format dynamically when report runs. I provided something like this Minute(Field!Column1.Value - Field!Column2.Value)) . But it gives #Error in report column.

Can anyone help me to write expression for this requirement.

Thanks

Sri

Developer