Prevent insertion of data from a currency edit which has no value.

There are a few issues at play here.
For example, how are you inserting the value? Is it byusing a data-aware currencyedit, e.g. a DBCurrencyEdit?
Or are you inserting it programmaticaly using SQL as in INSERT INTO Table etc.
Or are you saying MyADOQuery.Insert, then MyADOQUery.Fieldbyname('FieldName').value := Currencyedit.value;
Next is the database itself. You're using access. Have a look at the field in design view and check things like 'default value'
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Generally in the world of databases, NULL is different to 0. So if you DON'T insert a value into that field, by default the value should be NULL (or empty). However, there are several things that can happen when you insert a record that could pass a value of 0. For example if the field has a default value (database-side). Or if the insert takes place using a data-aware control, where the TDBCurrencyEdit might be inserting the value of 0. A default value can also take place from a dataset instance, using persisitent fields.
Hope that helps  

oh to be clear:
another possibility is if one of your data-aware controls is READING a null value as 0.00, such as a DBCurrencyEdit. (Or as explained, the value might not actually be Null, in which case you have to find out what's storing it as 0 instead of null)

I am using cxCurrencyEdit (devexpress)
and inserting
INSERT INTO Table etc. using parameters
like ...ADOQuery3.Parameters.ParamByName('a11').Value := cxCurrencyEdit12.Value;
in the DB it has no default value just Format:Euro;

 

Then it seems to me that your problem is on that line.
Rather get it to check if the value is null or empty, something like
if cxCurrencyEdit12.asstring = '' //then its null / empty
or
if length(cxCurrencyEdit12.Text) < 1 //then its empty
then store the value as null, e.g.
 ADOQUery3.Parameters.ParamByName('a11').value := null;

The queery is as big as it is...It would be too much work to go checking every single currencyedit.
also cxcurrencyedit has no asstring property.