Forms and Approvals based on response in the form

Hi. We are working on a new form and approval process where we want the approval to go to a manager defined in one of the fields on the form. This form will be used to approve employees floating to another department and the approval should first go to the manager specified in the form as the Float To Manager. Has anyone ever built an approval process based on a value in a field on the form? Any guidance would be appreciated. Thank you!