How can i create a matrix from the user input from seperate numeric field entries?

I am trying to perfrom a convolution operation by letting the user input the 3*3 kernel. But i am getting a filter error saying that the input data type is wrong. How can I solve this?

[dpb]

W/O the actual code pertinent to that part of the problem it's difficult to say for sure, but most likely you're not converting the text from the text box to numeric values before passing it to filter2