Index using a defined name array

[Swimmer1500m]

I have defined 3 arrays using DefineNames:
Boys_11_12
Boys_13_14
Boys_15_16

I then have defined a Combo dropdown with the following choices:
Boys_11_12
Boys_13_14
Boys_15_16

When the user selects the Boys age group using the Combo dropdown,
then use the selection in an Index function:
Index(Boys_(one of the three),...)

I get an error when using the Combo dropdown, but it works fine when
type in the array name directly into the Index function. Its as if i
knows the array when typed in, but not using the Combo dropdown.
created the Combo dropdown by typing in the array names into cells a
text, then using properties select where the dorpdown text is

 

[Bob Phillips]

Try

=INDEX(INDIRECT(G1),...)

where G1 holds the selected value in my case