Changing sample times from continuous or constant to discrete

I am experiencing the following error in my simulink model, Simulink version 7.6

"All sample times for 'onlineclassifier/Enabled Subsystem/bufferSampW' must be discrete. No continuous or constant sample times are allowed"

I am loading a 50X231 matrix that has in the first row the time samples (so in reality is 49X231), with 231 sample times. I am trying to read one column of the matrix at a time after an external trigger and use it for a matrix multiplication. The problem is that this matrix is loaded in continuous time and I have not been able to convert it into a discrete time matrix.

How can I do this?

I only need to use the matrix for a period of time given by the external event. This is a fixed matrix for all the simulink session.

any input is highly appreciated.

Thanks.