Declaramos la función :

Declare Function SHFormatDrive Lib "shell32" (ByVal hwndOwner As Long, _
        ByVal iDrive As Long, ByVal iCapacity As Long, ByVal iFormatType As Long)
        As Long


Parameters:

     hwndOwner
     Handle of the owner window for the dialog box.

     iDrive
     Value specifying the zero-based system drive index (A = 0, B = 1, etc.).

     iCapacity
     Value specifying the formatted capacity of the drive, the corresponding item
     is selected in the Capacity combo box.

     Win95:
        SHFD_CAPACITY_DEFAULT = 0 ' default drive capacity
        SHFD_CAPACITY_360 = 3 ' 360KB, applies to 5.25" drives only
        SHFD_CAPACITY_720 = 5 ' 720KB, applies to 3.5" drives only

     WinNT(?)
        ...?

     iFormatType
     Value specifying the format operation, the corresponding option button is
     selected in the Format type group box.

     Win95
        SHFD_FORMAT_QUICK = 0 ' quick format
        SHFD_FORMAT_FULL = 1 ' full format
        SHFD_FORMAT_SYSONLY = 2 ' copies system files only

     WinNT
        SHFD_FORMAT_FULL = 0 ' full format
        SHFD_FORMAT_QUICK = 1 ' quick format

Return values

     Win95
        -3 failure, drive can't be formatted (either doesn't exist or contains files in use by Windows)
        -2 operation cancelled
        -1 operation attempted but completed unsuccessfully
         6(?) operation completed successfully

     WinNT
        -1 dialog was shown
         0 error, dialog not shown

SHFormatDrive también puede ser pasado a rundll32 y ejecutarse mediante el shell :

Dim l As Long
l = Shell("rundll32.exe shell32.dll,SHFormatDrive")

pero no parece que funcionen los parámetros.