Change the data type after getting the cell value from a row below with index

Hello everyone

I have the following problem:

Sample Table:

In the sample table, you see 2 different types of row: Date or Message

My Goal is to get the Text cell from the Message-Row on the same row as the date

So I made a custom column using the index:

=if [Index] > 0 then Tabelle1[Text]{[Index]} else 0

Now if I want to change the datatype from my Text column so to date, so I can have only date values, I get this error: Expression.Error: A cyclic reference was detected during evaluation.

Can someone help me?

Or you may have a better idea to get the cell value?

Thank you