Here's some tips that may or may not apply here:
Dim CContentValue - always type your variables. For the benefit of others who may follow you, type it explicitly and eliminate uncertainty. When I read that, I wonder if you know it's a variant or not - especially when you seem to see a need to verify with a message box. Further, your test will return a value for type text if the control contains a string (including zero length string; i.e. "") but variant if it's Null.
Me![Text133] No, Me.[Text133]. If a control with that name doesn't exist on the form, you won't catch it in a code compile - no error until a run time reference to it occurs. A bad way to catch mis-spelled names.
Mid(Me![Text133], 3, Len(Me![Text133] - 2)) I read this as you want everything after the first 2 characters. If you don't specify a length for Mid, you get everything after the start point, so no need to worry about calculating the length: Mid(Me.[Text133], 3)
However, it is not accepting the Mid() into the CContentValue and says it is a data type mismatch?
Your count could be off in some cases or the control may be null. Regardless, the message means the data involved does not fit the type expected.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.