OK...then somewhere (either in the dataset, or wherever the source definition is), something is defining the layout and data types.
If you have data that normally is defined as numeric (currency amounts, etc.), then you might want to look at where it's initialy being defined/'read in' as a string. But if it's data that's normally alphanumeric but you want to treat it as numeric for a particular report, then you might want to look at the type conversion functions in the crystal formula editor.
If that info doesn't help, can you post some specifics about this dataset/schema and how it's being created?
Thanks,
Kevin