How To get Value Between Two drop down list

Question

i have two Dropdown list

 

From

Any

FL

IF

VVS1

VVs2

VS1

VS2

SI1

SI2

SI3

I1

I2

I3 

To

Any

FL

IF

VVS1

VVs2

VS1

VS2

SI1

SI2

SI3

I1

I2

I3

Now if User Select 'FL' in From and 'I2' in To than i need All Value in between two selected parameter.
like string values = "FL,IF,VVS1,VVs2,VS1,VS2,SI1,SI2,SI3,I1,I2";

How can i ?

Thanks in advance.