searchString - any text expression or text field representing the set of characters you want to find.
start - any numeric expression, or field containing a number, representing the number of characters from the start of the text string at which to begin the search.
occurrence - any numeric expression or field containing a number, representing which instance of the text string you want to find. A negative occurrence value causes the scan to go in the opposite direction from start. A zero value for occurrence is invalid and returns a result of zero.
This function is not case-sensitive. If searchString isn’t contained in text or if there was no specified occurrence, zero is returned.
Left(Name;Position(Name;“ “;1;1)-1) returns
William, when Name is a text field that contains William Smith.