string string1 = "This is an example string and my data is here";
string toFind1 = "my";
string toFind2 = "is";
int start = string1.IndexOf(toFind1) + toFind1.Length;
int end = string1.IndexOf(toFind2, start); //Start after the index of 'my' since 'is' appears twice
string string2 = string1.Substring(start, end - start);