Need UDF to delete duplicates from same context

Hi friends,

I was trying to write an udf to delete the duplicate values from same context but couldn't get any success.

Source Data

V1
V1
V2
V2
V3
Context Change
V1
V1
V6
V9

I want Result As:

V1
V2
V3
Context Change
V1
V6
V9

I Cannot use CollapseContext because I need to maintain the ContextChange as it is.

Thanks in advance.

Regards,

Sarvesh