How do you generate conditional output for a multi-variable hyperbolic function given changing slope?

I’ve been able to calculate q for t = 0:14399 and b = 1:0.1:2 simultaneously, however, I would like to control the calculation of q subject to several constraints (listed below). I’ve tried a number of methods and have yet to figure this out. Any and all help would be much appreciated. The constrains I want to impose on the function are below and my code is below that.

Thanks in advance!

Constraints

If qt-1 < qab then qt = 0, otherwise:

for (qt / qt-1) -1*360 < = -0.05 --> q = hyperdecline(qi,B,di,T)

for (qt / qt-1) -1*360 > -0.05 --> q = qt-1 * (1-dt/360)

Code

hyperdecline function

function q = hyperdecline(qi,B,di,T)
q = qi*(1+B.*di.*T).^(-1./B);

%INPUTS
% qi = IP rate (initial 24-hr production rate)
% di = initial decline rate (nominal)
% b = B-factor (constant)
% t = time period range (normally days) from 0 to n
% qab = production abandonment rate
% dt = terminal decline rate (exponential)

%OUTPUTS
% q = production at time t
% qcum = cumulative production at time t
% qm = monthly aggregation of q data using 

% Type curve inputs
qi = 20000;
di=.01;
b=1:0.1:2;
t = 0:14399;
qab=500;
dt=.05;

% Curve Calculations
[T B] = ndgrid(t,b); % Create grid of t and b values to iterate over
q = hyperdecline(qi,B,di,T);
qcum = cumsum(q);
qm = squeeze(sum(reshape(q',size(b,2),30,[]),2))'; % Aggregate q into 30 day months