In reality, I have about 15 different formats. The one you asking looks:

IF (@dateformat = 8)

 begin

 set @converteddt =

  RIGHT('0' + CAST(DATEPART ( hh , @datevar ) AS VARCHAR(2)), 2) +  ':' +

  RIGHT('0' + CAST(DATEPART ( mi , @datevar ) AS VARCHAR(2)), 2)

  set @formatexists = 1

 end

I don't have #7 but it can be done similar way with CASE statement or conversion of datetime variable to varchar first based on the formatting parameter.

I can make it Monday. I don't have SQL Server installed on my computer now.