Here an example: {{SetString1} ThisIsAText {{MessageBox {{InStr 1 | {{String1} | Is }
Result: 5 -- means "Is" starts at the 5th caracter in this string.
Here the text from the manual:
{{InStr
This command Returns the position of the first occurrence of one string within another. Syntax: {{InStr StartNumber | String being searched | String sought. Example: {{MessageBox {{InStr 1 | Recorder | der} Result: 6. If nothing is found a zero is given back.
See also the hints in chapter: Mathematical and string commands.