When you click debug in the error message box which line is highlighted?

Does the Combo Box have an ID as the bound column? You may have to access the Combo Box's Column property.

Also consider using Else If instead of individual If blocks. Each of them will have to be evaluated even if the item is found in the first block.

Example:
    If SpanType.Column(1) = "Arch" Then
        ShowandTellSub!Selection = "Arch"
    ElseIf SpanType.Column(1) = "Beam" Then
        ShowandTellSub!Selection = "Beam"
    End If

Thanks Kevin. The SpanType field does not have it's own ID. I could have set it up that way but I didn't because it is one of many fields in my form and the bridges main form is one of fourteen mains (roads, parks, buildings, culverts, etc).

I did try the else if and may go back to that.

When debugging, the line that is highlighted is the one I have selected in the combo box.

Also, I'm using the "on click" property and I wonder if I should try something else?

Problem solved! I'm not sure why, but I decided to delete the form control "SpanType" and redo it. Viola! No error message. Thank you are for trying to help me through this!

The "field '[1'" error usually indicates an unqualified name somewhere.  It is admittedly a confusing-looking error message, one of many quirks in Access.

If your code is in the main form, and you want to reference the subform "ShowandTellSub", your code should be:

     [ShowandTellSub].Form.[Selection] = ("Arch")

because the name "ShowandTellSub" is just a subform *control*; you need its "Form" property to reference the actual subform itself.

If your code is in the subform, it should be:

     Me.[Selection] = ("Arch")

You cannot just use the subform name "ShowandTellSub" to subtitute "Me" here.  Using the name "ShowandTellSub" means you have to fully qualify it:

     Forms!MainForm![ShowandTellSub].Form.[Selection] = ("Arch")

In short, the code [Subform Name].[Field Name] is wrong no matter where you use it.

P.S.:

You can shorten your entire code to just:

     [ShowandTellSub].Form.[Selection] = SpanType

No need to use If...Then to check for validity of the individual values.  The valid values are already specified inside the combo box.

No need to use .Value for the combo box, in most cases.  The rare case to use it is when you are typing inside and changing the combo box's content, in which case .Value is the original value before the change, and .Text is the value you are seeing as you are typing.

Also, no need to enclose strings with parentheses.  Just write "Arches" instead of ("Arches").