You can do it only after passing Diploma. You should send a form regarding this to IEI, Kolkata.
A Technician member, after acquiring diploma level qualification, changes his membership to Senior Technician, s/he shall be considered, on request, as exempted from Section 'A' Examination, provided s/he has secured exemption (obtained Grade 'C' or above with minimum GPA being 6) in four common subjects of same nomenclature in both Section 'A' (Non-diploma) and Section 'A' (Diploma) of revised syllabi.
No pass grade card of Section 'A' shall be issued. S/he shall be eligible to register for Section 'B', with requisite fee, with an undertaking that s/he shall not claim pass grade card for Section 'A'. The CGPA shall be calculated only on the basis of Section 'B' Examination, project work and laboratory experiments.
In case the Technician Member secured exemption in one or more common subject(s) of same nomenclature in both the schemes of revised syllabi, grade in common subject(s) can be carried forward, on request, after change of her/his membership.
You will not get Section A marks sheet. In the certificate - "Section A was exempted" will be mentioned. This may trouble while applying for job!