Try the code below. Persoanlly, I use text boxes and set the code to kick off under After Update, but you can add a button that will initialize. The '*' around the Text Box name will allow for broader seraches or searches where users might not know the whole name.
Code:
Me.FilterOn = False
Me.Filter = "[YourFieldNameHere] Like '*' &[Forms]![YourFormNameHere]![YourTextBoxNameHere] & '*'"
Me.FilterOn = True
Me.Requery
I also put a "Clear Filters" button with the code below on my forms
Code:
Me.TextBox1 = Null
Me.TextBox2 = Null
Me.FilterOn = False
Hope that helps.