Question: find zeros in a complicated function


I'm having serious problems in finding and saving the roots of this equation:

((.642*(-1.*BesselJ(2.250000000*m+1., 0.75e-2*a)+299.9999999*m*BesselJ(2.250000000*m, 0.75e-2*a)/a))*a-10.*BesselJ(2.250000000*m, 0.75e-2*a))*BesselY((9/4)*m, 0.2e-1*a)-((.642*(-1.*BesselY(2.250000000*m+1., 0.75e-2*a)+299.9999999*m*BesselY(2.250000000*m, 0.75e-2*a)/a))*a-10.*BesselY(2.250000000*m, 0.75e-2*a))*BesselJ((9/4)*m, 0.2e-1*a)

a is a eigenvalue and there exists infinity eigenvalues for each m. If we consider p as the n-th eigenvalue for each m, results in: a(m,p).

Is it possible to solve this analytically, or do I have to do it numerically? How? I tried with nextzero but in several ocasions I got FAIL. 

In order to use this eigenvalues in further equations, what's the best way to use them? To built up a matrix with m,p regarding to rows/columns, for example?

Thank you so much!

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