Change sample values from a buffer automatically?

Hi! So, I was once messing up with the waveform~ help, when I realized I was able to draw my own wave in the graph. Since I realized it was possible to change the sample values of an audio file, I wondered if it could be possible to make a program that changes those values wiht number inputs rather than mouse selection. Basically what I want is to make a program that chooses by itself the range of samples to be altered (can also be miliseconds) and change the value to the one given in the program. I already made all I needed to get both the range of samples altered and the value I wish to apply to the selected samples, but I cannot find the way to make them work.

Summarizing, is it possible to change the sample values inside a buffer through numbers inputs?
Thanks.