: I have a simple  form with a two option  buttons op1 and op2.
: Selecting op1 should execute  the following lines  of code

No. Clicking on the CommandButton1 button should execute
your lines of code. To execute these lines on a change of op1
you would need this.

Private Sub op1_Change()
Dim plate As Boolean
Load Frm
Frm.Show
plate = Frm.op1.Value

If plate = True Then
LookAhead = 110
Else
LookAhead = 93
End If
End Sub

Or perhaps:

Private Sub op1_Click()
Dim plate As Boolean
Load Frm
Frm.Show
plate = Frm.op1.Value

If plate = True Then
LookAhead = 110
Else
LookAhead = 93
End If
End Sub

Neither one of these makes sense because Frm is already
loaded and shown (otherwise op1 could not be clicked).


: however, I am getting an error  Object variable  or With block
: variable not set  error.

You should be getting a "form already shown..." error.
Perhaps you are not showing us enough code.