Instead of a command button calling an input box you can have a command button call the Find Dialog box (the one with the Binoculars as an icon). Your code would look something like this:
Private Sub cmdSearchPart#_Click()
Me.Controls("Part#"

.SetFocus
SendKeys "%ha%n", False '** This line makes the find
' dialog box default to Match
' "Any Part Of Field". If you
' want the user to have to enter
' the exact Part#, leave this
' line out.
DoCmd.DoMenuItem acFormBar, acEditMenu, 10, , acMenuVer70
End Sub
I think this will get you what you want!! Good luck!!