Conditionally showing enum values

[Pointer]

Hello;
With respect to conditional display, [item1]: number is [item2]: when enum (A, B, C, D);

ifs [item1] = 10, [item2] = A and B (show),
ifs [item1] = 20, [item2] = C and D (show)

how can I do this, so not all values will be shown in enum