Making a user input a matrix

I'm trying to create a function in where a user can input 1 to have an excel file of two lines of data read as (x,y) coordinates. But also that the user can select 2 so they can enter their own (x,y) coordinates but in comma-separated pairs. Like pairs in 2 rows. Whenever I try to enter values for z I only get an empty matrix and idk how to actually fix that. Would I need to do a loop or another function like creating a cell array? (After the matrix is created I'm also hoping to just read each row and attach them to either x and y).

if true
  % code
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function [x,y] = BB_GrabInputData(z)
%Creates an output of data depending on what the user inputs for vectors
%   User must select either file or manual data points in an even-numbered
%   vector
A=0;
while A == 0
  User_DataSelect=input('<1>Read in a data file or <2>Enter data points by hand?' );
  if User_DataSelect==1
      z = xlsread(strinput('Enter in your file name'));
      x = z(:,1);
      y = z(:,2);
      A= A + 1;
  elseif User_DataSelect==2
      disp('Enter in your data points in comma-seperated pairs.\n Press <Enter> without typing any numbers when you are done entering the data.\n')
      z = input('');
      z = z(end) + z

        A=A+1;
else
    disp('Error: Invlalid User Input') %Detects when an invalid selection occurs and the loop repeats
    A=0;
    end
end
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

[Stephen23]

Rather than using input it would be much simpler to call uitable.

[Brevon Baker]

The user needs to be able to input their data points in comma-separated pairs.

Answer 1

[Stephen23]

x = [];
y = [];
pmt = 'Enter comma-separated pairs. Press <Enter> with no data to exit. ';
while true
    str = input(pmt,'s');
    if numel(str)
        tmp = sscanf(str,'%f,%f');
        x(end+1) = tmp(1);
        y(end+1) = tmp(2);
    else
        break
    end
end

[Brevon Baker]

I can't seem to even run this program.

[Stephen23]

@Brevon Baker: I fixed the start conditions, it works now:

Enter comma-separated pairs. Press <Enter> with no data to exit. 1,2
Enter comma-separated pairs. Press <Enter> with no data to exit. 3,4
Enter comma-separated pairs. Press <Enter> with no data to exit. 5,6
Enter comma-separated pairs. Press <Enter> with no data to exit. 
>> x
x =
     1     3     5
>> y
y =
     2     4     6