Creating an event in CRM - cannot link to contact

Creating an event in CRM - cannot link to contact

Hi Team. I am not sure if I am doing something wrong. 

I am pushing contacts from Creator to CRM. After sending the contact across I extract the Contact ID into a field in ZC. I now want to create a task and an event in the CRM system against this new contact. 

If I create a new task, it does not link it to the contact (even though I have set the "Who ID" field to the extracted Contact ID field variable. In events, it does not even allow me to select the Contact ID field against the "Who ID" field as it is not a string value. If I convert it to string using cstring, it still does not work.

Can you please let me know how to create tasks and events in CRM from Creator?
Thanks
Jaosn