strfind when I have more than one row

You have a couple of choices with STRFIND. You could loop over the rows, or pad the array with NANs (or other irrelevant value) then reshape to one long string. For example:

A = [1 2 3 4 5 6;7 6 5 6 3 2;1 2 3 4 5 6]

for ii = 1:size(A,1)
    L{ii} = strfind(A(ii,:),[5 6]); % Preall if large A.
end

B = [A nan(size(A,1),1)];

strfind(reshape(B.',1,[]),[5 6])

a=['Congratulations'
    'to Walter      '
    'for his 4000   '
    'reputation     '
    'points         ']
rc=[];
for r=1:size(a,1)
    c=strfind(a(r,:),'Walter');
    if ~isempty(c)
        rc=[rc; r c]; %just in case the word appears multiple times
    end
end
rc %first column is the row and second column is the column where the word is

STRFIND works on cells too:

a=['Congratulations'
    'to Walter      '
    'for his 4000   '
    'reputation     '
    'points         '
    'WalterWalterWal']

pat = 'Wal'

strfind(cellstr(a),pat)

This is a possible solution ... not perfect though:

%
% Look for a in b. Returns cell array of 
% strfind results for each row.
%
% Usage: strfindmultirow(<searchdata>, <searchpattern>);
%
% e.g. if:
%
% a=['Congratulations'
%    'to Walter      '
%    'for his 4000   '
%    'reputation     '
%    'points         ']
%
% rc = strfindmultirow(a, 'a');
%
% yields:
% rc = strfindmultirow(a, 'a')
% ans = [1x2 double]    [5]     []    [6]     []
%
function rc = strfindmultirow(a, b)

rc={};
for r=1:size(a,1)
    c=strfind(a(r,:), b);
    rc{length(rc) + 1} = c;
end