[AccessD] Good Code Bad Code Question

The following line of code works correctly
 
Me.txtCost.Value = Me.cboPartNum.Column(2)
 
 
When I try to compile the code I get an error message that .cboPartNum    
 
Method or Data member not found.  Any Idea what is up?
 
Option Explicit is set
 
Thanks
 
 
Joe Hecht
Los Angeles CA