Color transformation from LAB to CMYK

I have an .icc profile that containts the data to transform from LAB to CMYK.

profile.Header
  struct with fields:
                  Size: 6786792
               CMMType: 'MSFT'
               Version: '4.2.0'
           DeviceClass: 'output'
            ColorSpace: 'CMYK'
       ConnectionSpace: 'Lab'

Now, we measure the LAB values in Photoshop and then see what the according CMYK values are using the Eyedropper tool. This is very tiresome work as we need to do it for hundreds of colours. Therefore, I would like to use the

makecform

and

applycform

functions to execute this transformation. I do not seem to succeed though, as Matlab always seems to require both an input and output icc profile, but I only have one? I don't see how I can use the makecform function to execute this simple step. There is no premade LAB-CMYK function available as far as I found out.