How to copy a value of certain Dataset into formula in Macro

The problem itself was on Subject-field. But here is some extra-information:

I have a large number of files, and a certain style to analyze them.

I have a macro which has one value, which has to be equal to a value from one dataset (=only one value) This value changes, depending on the file.

How can I have a macro which goes into dataset and copies the first value to itself… Or something equivalent to this.

Best Regards,
Kari