SQL Updating Rows Without Knowing Column Name

SQL Updating Rows Without Knowing Column Name

I am attempting to create a stored procedure that will update a specific
row and column location based on user input. My table has approximately
100 columns utilizing names in progressive increments. Ex Page1, Page2,
Page3, Page 4.... etc. The data must also be updated in progressive
increments as users finish different versions of each page.
When the procedure is called I need it to find the user's row(Page1 is the
key and unique), and put the information in where their version of the
file is saved into the first NULL column. I have seen talk about using
cursors for similar applications but I am not sure if this is the proper
solution.
----------------------------------------------------
| Page1 | Page2 | Page3 | Page4 |
----------------------------------------------------
| /pg1.htm | /pg2.htm | /pg3.htm | NULL |
----------------------------------------------------
| /pg1.doc | /pg2.doc | NULL | NULL |
----------------------------------------------------
| /pg1.pdf | NULL | NULL | NULL |
----------------------------------------------------
I need the procedure to update the row sequentially each time with one
piece of data when it is called. My issue is in making this scaleable
instead of limiting it with 100 + IF statements.
The pseudo code I cooked up looks like this but is terribly inefficient:
FIND ROW that matches unique key
LOOP Find_NULL
IF Column2 == NULL
UPDATE DATA HERE
ELSE IF Column3 == NULL
UPDATE DATA HERE
ELSE IF Column4 == NULL
UPDATE DATA HERE
ELSE IF.... and on and on
END LOOP Find_NULL
I am utilizing MySQL which I have been told does not support Dynamic SQL.
I attempted to create a variable and modify it as I went through the data
to store the next NULL column however this did not work.
If anyone has any solutions or advice I would appreciate it.
Thanks in advance.