[NTG-context] How to draw a red frame of a row in a matrix?

Dear all, I made a matrix as follows and I'd like to draw a red frame over the i-th row in a matrix. \startformula \startmatrix[left={\left (\,},right={\,\right)}] \NC a_{11} \NC a_{12} \NC \dots \NC a_{1n} \NR \NC \vdots \NC \vdots \NC \vdots \NC \vdots \NR \NC a_{i1} \NC a_{i2} \NC \cdots \NC a_{in} \NR \NC \vdots \NC \vdots \NC \ddots \NC \vdots \NR \NC a_{m1} \NC a_{m2} \NC \cdots \NC a_{mn} \NR \stopmatrix \stopformula But \frame or \inframe is not working inside matrix. Is there a way to do that? Thank you. Best regards, Dalyoung