Extension rule - csentry for AD disinguishedName

I have to write rules based on the csenty of the distinguishedName of the accounts in AD.

for example -  distinguishedName contains OU=XYZ, do this. if DN conatins OU=abc, do this.something like

if(csentry["DistinguishedName"].value.contains("ou=users")){ do this}

Can someone help me in how to use contains function for DN csentry? Also, do I have to flow the distinguishedName in attribute flow? I don't need to pass this to MV. Just need to read the value of DN and calculate values based on that.

TIA.