I suggest you go for the DFT-D3 method, which has official parameters for a number of GGA functionals, including PBEsol. If you look at Table 25 in the ATK reference manual (
http://www.quantumwise.com/documents/manuals/latest/ReferenceManual/index.html/ref.grimmedftd3.html), you will see the parameters to use. However, as stated in the text above the table, the VNL scripter supports setting the parameters for PBE, BLYP, and RPBE. So for PBEsol you need to set it manually:
1) Choose standard PBE and Grimme DFT-D3, and change the DFT-D3 parameters to match PBEsol and turn off the "three-body term" (see attached PNG).
2) Save the script and open it in an editor, and manually change from GGA.PBE to GGA.PBES.
