output strings to specific positions in a file

Been searching for about 3 hours for similar functionality that I can get examples of how to output text from variables into certain locations in a file. I would like to incorporate this into a script. I have not been able to find a command example that does it all in one method. I find part of it in sed, part of it in awk....etc.

What I am trying to do is prompt a user for some text. Then from a config file I will pull some X and Y coordinates for where to place the text in the file. I might have to loop a couple times to place more than one string to the respective location.

Example:
prompt user for text string one. the script will determine that this string should be put in the Nth line (let's say 2) and should start at the Nth space (let's say 10). For string two let's just say the values are line 4 and space 3.

essentially I am hoping to make a file that could basically be printed like a form from some user input and some known info from a config file or generated from the script. I would like to use KSH for the script. I guess any sed or awk solutions would be ok. Not sure what else could do this efficiently.

Thanks in advance!

So I would expect to get some output like:
---------------outline of output file--------------
|
| First string
|
| Second string

Maybe, your paradigm is tricky. Is it sufficient to make a new file with parts of the old files selected by head or tail options?

Updating a file in place not at eof is the realm of a language like PERL or C. For instance, in C you can mmap64() the whole file and then just write it like a char[].