The Color Conversion C API provides a color space dialog that can be used to initialize a conversion. To do a dialog based initialization follow the steps below:
Dim RGBData(100) As Byte
Dim LABData(100) As Byte
Dim nWidth As Integer
Dim nHeight As Integer
Dim nInAlign As Integer
Dim nOutAlign As Integer
Dim ClrHandle As Long 'color handle
Dim cnvParam As CONVERSION\_PARAMS
L_ClrDlg DLG_LAB, Form1.hWnd, ClrHandle, cnvParam
L_ClrConvert ClrHandle, RGBData(0), LABData(0), nWidth, nHeight, nInAlign, nOutAlign
L_ClrFree ClrHandle