Problem with view Column formula

I have the following column formula :

@If(DepartureDate1 = “” ; AccDepartureDate1 ;DepartureDate1 ;

DepartureDate1 = “” & AccDepartureDate1= “” ; “Unknown”)

The syntax is accepted ok, but the column results return , “Error Invalid data type for operator” all the fields are Text.

Can i have the & in a column formula ?? for text if not what fo i use ??

Thanks

Subject: Problem with view Column formula

I don’t think the syntax is ok, because:

@If(DepartureDate1 = “” ; [this is your condition]

AccDepartureDate1 ; [this is the true branch]

DepartureDate1 ; [this is your second condition?] <======

DepartureDate1 = “” & AccDepartureDate1= “” ; [this is your second true branch]

“Unknown”) [this is the last false branch]