Returns the location of the first occurrence of a string within another string.
INSTR([ start_position ], search_string, substring)
INSTR returns the character position of substring within search_string.
start_position is the character position within search_string where the search should begin. If you omit start_position, INSTR begins as position 1.
IF INSTR locates the substring, it returns an index to the starting character. Otherwise, INSTR returns 0.
PRINT "RING in SUBSTRING", INSTR("SUBSTRING", "RING")
PRINT "X in STRING", INSTR("STRING", "X")
Results in:
RING in SUBSTRING 6
X in STRING 0