Search In Certain Field

I want to built in an search button on the form in order to find records with the desired value in a certain field of the record. the caption of the textbox I want to search in is "NombreSTL" and the code below doesn´t work. whats wrong? thanks in advance...

Private Sub search1_Click()
On Error GoTo Err_search1_Click
Dim strWhere As String
strWhere = "NombreSTL"

Screen.strWhere.SetFocus
DoCmd.DoMenuItem acFormBar, acEditMenu, 10, , acMenuVer70

Exit_search1_Click:
Exit Sub

Err_search1_Click:
MsgBox Err.Description
Resume Exit_search1_Click

End Sub