what's wrong with variable in VBA calling amibroker.import

[fishmarket]

There are two command below in VBA to import a designated Csv file into amibroker, however one is able but the other is not.

The one is hardcoded the filename and format filename is ok. but the one use variable is not ok, what's wrong? I need to use variable.

dim strFormatFile as string
strFormatFile = "o120_13Apr.Format"
lresults = Amibroker.Import(iType, "C:\Ami\Temp\D130717_1818.csv", strFormatFile) -> not ok
lresults = Amibroker.Import(iType, "C:\Ami\Temp\D130717_1818.csv", "o120_13Apr.Format") -> ok

please help