How to change output of stored procedure on the fly in this query?

I am trying to achieve something which I think is simply, but yet the syntax escapes me

Here's the query:

SET @T02_IDENTIFIANT_DSC = 'Hello ' + @Compagnie + ' '
INSERT INTO @TableDonnees
EXEC THE_DATABASE..spHeader @ValDate, @ValDate, '65', @T02_IDENTIFIANT_DSC, @RecCount

spHeader returns a record with two rows. How could I catch the value of one of the rows, modify it, then proceed to the INSERT ?

Thanks