Pulling data from different workbooks and collating on another

Hello,

I would like to be able to do the following; have a number of work books which are allocated to team members (x4) which they complete with various pieces of information. As a manager I have a work book which collates all the information from all 4 work books on to mine so I can sign off as actions taken as checked and complete.

I was thinking is it an "IF" formula but can't seem to get it right.

Thanks for any help