How can i extract the values of Input in my S function

Hello Everyone. I'm using two inputs u1 and u2 in my s function block and i want to extract these values in my C file to develop CMEX file. I used the following C code real_T Psi_k_l[2][1]={-u2[k],u1[k]}; Here both inputs have 1000*1 dimension in work space. If i took k=5; then there is no value of u1 and u2 in the matrix but workspace has values. please tell me which command i need to use to extract the values in my C function from simulink model or workspace? Thank you so much