I'm not sure whether it will work with Excel 2007, but I've already attempted that approach in Excel 2010. It doesn't work for me. Once the import dialog box is up, the script stops. Using a timer to call another sub in the same module to appactivate and sendkey will only resume to work if the dialog opened initially from the 1st sub is closed and re-open manually. Well, either that or the VBE throws an error because window not found - depending on how you code it.
For whatever technical reasons - either in SAPGUI or Windows or Excel, the only way to do this is to run the subroutines from two different process instances with the first script calling the second script before it calls the dialog box. You can use either VBA in two different Excel files, VBA and VBS, VBS and another VBS or two instances of script process of whatever scripting languages you prefer.
I believe Scriptman used 4 different VBS to do it - one to call the dialog, two to sleep for 0.1sec and 1sec and another to appactivate and sendkeys.