Ho do I use Interp1 together with ODE45?

I am using the ode45 solver in the function:

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function Mdot_s = HKode(t, ms_HK, T_bulk, k_so, k_sf, m_fuel)
m_fuel=interp1(T_bulk,m_fuel,t);  
k_sf=interp1(T_bulk,k_sf,t);      
k_so=interp1(T_bulk,k_so,t);      
Mdot_s = (m_fuel.*k_sf)-(k_so.*(ms_HK));

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to solve for the time-dependent variable "ms_HK."

In the main code, "T_bulk" is a time-dependent vector with a few hundred values, and "m_fuel," "k_sf," and "k_so" (for brevity, lets refer to these collectively as "var") are calculated (in the main code)from "T_bulk," so they are vectors of equal length to that of "T_bulk."

----------------!!!The Problem !!!------------------

the interp1 values calculated for "var" are outside of the known vector values for "var."

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My understanding of the interp1 function was that it would interpolate between known values of "var" and "T_bulk" using steps of "t" defined by the ode45 solver to give a more refined vector of "var" values for use in ode45. Am I misunderstanding how interp1 is supposed to be used with ode45?

I call the function in the main code using:

[t, ms_HK] = ode45(@(t,ms_HK) HKode(t,ms_HK,T_bulk,k_so, k_sf, m_fuel),Tspan,IC_HK, options); % Solve ODE