Insert blank value based on another field

[Yaniv]

Hi,

I have a table named 'service'.

I want to create a new calucuated column that says if the field 'done' (date field) is blank do not insert any value but if the 'done' field is not blank insert the date value+one day.

Below what I already tried - 

1. NewColumn= IF(Service[Done]=BLANK(),BLANK(),Service[Done]+1) 

I get the error message - Column '' in Table '' contains blank values and this is not allowed for columns on the one side of a many-to-one relationship or for columns that are used as the primary key of a table.

2. NewColumn = IF(Service[Done]=BLANK()," ",Service[Done]+1)

Error message: Expressions that yield variant data-type cannot be used to define calculated columns.

Does anyone have an idea how to resolve it? I'm getting frustrated