How to get the value from ComboBox to strSQL in VBA?

I am trying to get value from ComboBox to strSQL, but I just have no idea how to do this.

My value of ComboBox is Mid(combobox, 6, 3)

I tried

strSQL = "Select * from schedule where FltNumber = Mid(combobox, 6, 3)" or

strSQL = "Select * from schedule where FltNumber = '" & Mid(combobox, 6, 3) & '""

and other many ways did not work.

Please help