Hey there
No it is not possible in any of the colleges of Delhi University to change from BSc Honours to BCA. If you get selected then you have to to pursue sem BSc Hons maths course in Delhi University. But if you don't want to do then you have to try next year.
For more details related to Delhi University click on below link:
https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.careers360.com/university/university-of-delhi-delhi/amp&ved=2ahUKEwjv-_bQ8IjzAhVH73MBHeukBdAQFnoECAMQAQ&usg=AOvVaw0RSGPaojjngT7npmHS3qIK&cf=1
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