how to write data to txt file (certain row)

[二子]

hello,every one,two questions need your help.

 1)in my computer,a txt file exist, i know the file name and the path,I want to write data to a centain row ,how to do? example: i want to write "123456"to 7th row in txt file(labview or vb).
2)in while loop, i want to control interval loop time ,how to do?
thank you ,very much. method is simple  better.for me.
 

[daveTW]

When the file content easily fits into memory, you can use the attached file. It is not appropriate to use the pick line function since you need the position in the string to insert the new string. I suppose, this function doesn't work properly when there are DOS linefeeds (0xA, 0xD), so you have to adapt the VI or the file string.
For the while loop use the timed loop from the Structures/Timed Loop palette.
Greets, Dave