Use the "scratch" function when you want to replace a string of characters, but you cannot specify its place (one place) in the text.
Function structure:
= Scratch ( 'cell in which you want to make a substitution'; 'old text'; 'new text')
An example of using the excel formula in practice:
In cell A1 we have the date written as follows:
2013 _ 10 _ 28
due to the hyphen of individual date components, the above entry will be treated as text. To change this, I will use the "scratch" function as follows:
= substitute ( A1 ; " _ "; " - ")
and I will get a record in the form of the date: 10/28/2013