For with in user variable error

Hello! I come to you for the following problem: in the query I need the "for" loop to go from 15 to 99 using user variables:

SET @v1 = 15; SET @v2 = 99; SET @v3 = 0;

DELIMITER //

FOR testing IN @v1..@v2 DO

SET @v3 =@v3 + 1 ; END FOR ;//

DELIMITER ;

But the server returns : "[Err] 1064 - You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '@v2 DO"

If I replace the variable @ v1 with the value 15, it works perfectly, but I need it to be a user variable.

What am I doing wrong and what would be the possible solution?

Thank you very much for your attention.