Insert decimal value into Currency Access field

Short background: I am replacing an outdated, Visual Based based program with a C#-based one. With the program comes an Access (JET) based database which is already in use. For now, I want to connect to the current database for practical reasons. However in the foreseeable future I'd like to replace it with SQL Server.

Question: The database stores financial information using the Access 'Currency' datatype. In C#, I use 'Decimal' to represent financial information. Naturally, I get an error when I try an INSERT or UPDATE-query to store the Decimal in the Currency-field (actually, I get an error once and with it, it automatically changes the datatype of that specific record to Decimal). I'm not sure what the best way to solve this problem is:

1. Transform the Decimal into Currency in my program and inserting it after. Is this even possible (C# says the values from the field are of the DBNull-type since it doesn't know Currency)? If yes, how do I do this?
2. Change the datatype of the field into Decimal. Will I risk corrupting financial information when I do this?
3. Any other/better suggestions?

Thanks in advance!

The exact error message:

System.Data.Odbc.OdbcException (0x80131937): ERROR [07006] 
[Microsoft][ODBC Microsoft Access-stuurprogramma]Inbreuk op kenmerk van beperkt gegevenstype

It's Dutch and translates to Restricted data type attribute violation

My UPDATE code:

public Boolean setFuelCosts(int rentID, Decimal fuelcosts)
        {
            string conString = lem2;
            string queryString = "UPDATE rental SET fuel = ? WHERE rentid = ?";
            OdbcCommand command = new OdbcCommand(queryString);
            command.Parameters.Add("@fuel", OdbcType.Decimal).Value = fuelcosts;
            command.Parameters.Add("@rentid", OdbcType.Int).Value = rentID;
            return factory.executeUpdateCommand(conString, command);
        }

public Boolean executeUpdateCommand(String conString, OdbcCommand command)
        {
            bool result = false;
            using (OdbcConnection connection = new OdbcConnection(conString))
            {
                try
                {
                    command.Connection = connection;
                    command.CommandType = CommandType.Text;
                    connection.Open();
                    int i = command.ExecuteNonQuery();
                    result = (i >= 1);
                    connection.Close();
                }
                catch (Exception exc)
                {
                    System.Windows.Forms.MessageBox.Show(exc.Message);
                    System.Windows.Forms.MessageBox.Show(exc.StackTrace);
                }
            }
            return result;
        }

Your issue appears to be a limitation of the Access ODBC driver when dealing with Currency fields using System.Data.Odbc in .NET. An OdbcDataReader will return those fields as System.Decimal (if the value is not NULL), but System.Data.Odbc apparently won't accept a System.Decimal parameter for a Currency field.

As a workaround you could replace

command.Parameters.Add("@fuel", OdbcType.Decimal).Value = fuelcosts;

with

command.Parameters.Add("@fuel", OdbcType.NVarChar).Value = fuelcosts.ToString("0.0000");

I just tested this from C# 2010 against an Access 2000 database file and it worked for me.