No, because dividing an INT by an INT results in an INT. If you want a floating point result, one of the sides of the division must be a float. You can try these options:
a# = Int(123.456) + (Int(123.456)/1000.0)
or
a# = Int(123.456) + Float(Int(123.456)/1000)
a# = Int(123.456) + (Int(123.456)/1000.0)
or
a# = Int(123.456) + Float(Int(123.456)/1000)