  We estimate the near-Sun axial magnetic field of a coronal mass ejection
(CME) on 10 March 2022. Solar Orbiter's in situ measurements, 7.8 degrees east
of the Sun-Earth line at 0.43 AU, provided a unique vantage point, along with
the WIND measurements at 0.99 AU. We determine a single power-law index from
near-Sun to L1, including in situ measurements from both vantage points. We
tracked the temporal evolution of the instantaneous relative magnetic helicity
of the source active region (AR), NOAA AR 12962. By estimating the helicity
budget of the pre-and post-eruption AR, we estimated the helicity transported
to the CME. Assuming a Lundquist flux-rope model and geometrical parameters
obtained through the graduated cylindrical shell (GCS) CME forward modelling,
we determined the CME axial magnetic field at a GCS-fitted height. Assuming a
power-law variation of the axial magnetic field with heliocentric distance, we
extrapolated the estimated near-Sun axial magnetic field to in situ
measurements at 0.43 AU and 0.99 AU. The net helicity difference between the
post-and pre-eruption AR is $(-7.1 \pm 1.2) \times 10^{41} \mathrm{Mx^{2}}$,
which is assumed to be bodily transported to the CME. The estimated CME axial
magnetic field at a near-Sun heliocentric distance of 0.03 AU is 2067 $\pm$ 405
nT. From 0.03 AU to L1, a single power-law falloff, including both vantage
points at 0.43 AU and 0.99 AU, gives an index $-1.23 \pm 0.18$. We observed a
significant decrease in the pre-eruptive AR helicity budget. Extending previous
studies on inner-heliospheric intervals from 0.3 AU to $\sim$1 AU, referring to
estimates from 0.03 AU to measurements at $\sim$1 AU. Our findings indicate a
less steep decline in the magnetic field strength with distance compared to
previous studies, but they align with studies that include near-Sun in situ
magnetic field measurements, such as from Parker Solar Probe.
