Is it a combobox from the control toolbox toolbar placed on a worksheet?
if yes, then here's one way:
Option Explicit
Sub testme01()
Dim OLEobj As OLEObject
With ActiveSheet.Range("a12:c12")
Set OLEobj = .Parent.OLEObjects.Add(ClassType:="Forms.ComboBox.1", _
Link:=False, DisplayAsIcon:=False, _
Left:=.Left, Top:=.Top, Width:=.Width, Height:=.Height)
With OLEobj
.ListFillRange _
= Worksheets("sheet2").Range("a1:a10").Address(external:=True)
.LinkedCell _
= Worksheets("sheet2").Range("b1").Address(external:=True)
End With
End With
End Sub