You will need to use a ComboBox from the Control Tool Box, not a Forms Control.

While in design mode, double click the control to bring up the Properties Window in the VBE. Look for the LinkedCell property and reference $A$10.

Then use this code for the control change event. It will write the same value to cell A11.
Private Sub ComboBox1_Change()
    Range("A11").Value = ComboBox1.Value
End Sub