It does not help how many conditions you add to the IF statement. The USE statement is interpreted at compile time, why you always get the error. Here is a quick example:

IF 1 = 9

BEGIN

USE nosuchdb

END

Output:

Msg 911, Level 16, State 1, Line 3

Database 'nosuchdb' does not exist. Make sure that the name is entered correctly.

One workaround is to wrap it all in EXEC(), but that would make the code impossible to read and maintain. Another is put this in a stored procedure, which you then can call with:

IF databasepropertyex(...) etc

BEGIN

EXEC archer.dbo.do_some_reindexingstuff

END