The replace() function allows you to overwrite characters in a string by replacing existing characters in the string.
replace(target, replacement, start, length)
• target – A string or string field containing the characters you wish to replace.
• replacement – A string you wish to replace characters in target with.
• start – The position in the target string where you want to put the replacement characters. Spaces are included in this length.
• length – The number of characters from the replacement string you want to replace characters in the target string with. Spaces are included in this length.