You need to add some code to the implementation of your IOleCommandTarget.QueryStatus, something like this (in C#):

int IOleCommandTarget.QueryStatus(ref Guid cmdGroup, uint cCmds, OLECMD[] prgCmds, IntPtr pCmdText)
{
    if (cmdGroup == yourCommandSet)
    {
        if (prgCmds[0].cmdID >= yourDynamicId && prgCmds[0].cmdID < (yourDynamicId + 16)) // suppose you want a maximum of 16 dynamic items
        {
            int index = (int)prgCmds[0].cmdID - yourDynamicId;

            OLECMDTEXT.OLECMDTEXTF flags = OLECMDTEXT.GetFlags(pCmdText);
            if (flags == OLECMDTEXT.OLECMDTEXTF.OLECMDTEXTF_NAME)
            {
                OLECMDTEXT.SetText(pCmdText, "yourText" + index);
            }

            prgCmds[0].cmdf = (uint)(OLECMDF.OLECMDF_ENABLED | OLECMDF.OLECMDF_SUPPORTED); // for example
        }
    }
}

Of course, the associated IOleCommandTarget.Exec must be also modified to correspond (using the same compute index).

The OLECMDTEXT is a pretty hacky utility class that can be found on various places on the internet, here it is:

/// <devdoc>
/// Helper class for setting the text parameters to OLECMDTEXT structures.
/// </devdoc>
internal static class OLECMDTEXT
{
    /// <summary>
    /// Flags for the OLE command text
    /// </summary>
    public enum OLECMDTEXTF
    {
        /// <summary>No flag</summary>
        OLECMDTEXTF_NONE = 0,
        /// <summary>The name of the command is required.</summary>
        OLECMDTEXTF_NAME = 1,
        /// <summary>A description of the status is required.</summary>
        OLECMDTEXTF_STATUS = 2
    }

    /// <summary>
    /// Gets the flags of the OLECMDTEXT structure
    /// </summary>
    /// <param name="pCmdTextInt">The structure to read.</param>
    /// <returns>The value of the flags.</returns>
    public static OLECMDTEXTF GetFlags(IntPtr pCmdTextInt)
    {
        if (pCmdTextInt == IntPtr.Zero)
            return OLECMDTEXTF.OLECMDTEXTF_NONE;

        Microsoft.VisualStudio.OLE.Interop.OLECMDTEXT pCmdText = (Microsoft.VisualStudio.OLE.Interop.OLECMDTEXT)Marshal.PtrToStructure(pCmdTextInt, typeof(Microsoft.VisualStudio.OLE.Interop.OLECMDTEXT));

        if ((pCmdText.cmdtextf & (int)OLECMDTEXTF.OLECMDTEXTF_NAME) != 0)
            return OLECMDTEXTF.OLECMDTEXTF_NAME;

        if ((pCmdText.cmdtextf & (int)OLECMDTEXTF.OLECMDTEXTF_STATUS) != 0)
            return OLECMDTEXTF.OLECMDTEXTF_STATUS;

        return OLECMDTEXTF.OLECMDTEXTF_NONE;
    }

    /// <devdoc>
    /// Accessing the text of this structure is very cumbersome.  Instead, you may
    /// use this method to access an integer pointer of the structure.
    /// Passing integer versions of this structure is needed because there is no
    /// way to tell the common language runtime that there is extra data at the end of the structure.
    /// </devdoc>
    public static string GetText(IntPtr pCmdTextInt)
    {
        Microsoft.VisualStudio.OLE.Interop.OLECMDTEXT pCmdText = (Microsoft.VisualStudio.OLE.Interop.OLECMDTEXT)Marshal.PtrToStructure(pCmdTextInt, typeof(Microsoft.VisualStudio.OLE.Interop.OLECMDTEXT));

        // Get the offset to the rgsz param.
        IntPtr offset = Marshal.OffsetOf(typeof(Microsoft.VisualStudio.OLE.Interop.OLECMDTEXT), "rgwz");

        // Punt early if there is no text in the structure.
        if (pCmdText.cwActual == 0)
            return String.Empty;

        char[] text = new char[pCmdText.cwActual - 1];
        Marshal.Copy((IntPtr)((long)pCmdTextInt + (long)offset), text, 0, text.Length);
        StringBuilder s = new StringBuilder(text.Length);
        s.Append(text);
        return s.ToString();
    }

    /// <include file='doc\NativeMethods.uex' path='docs/doc[@for="OLECMDTEXTF.SetText"]/*' />
    /// <devdoc>
    /// Accessing the text of this structure is very cumbersome.  Instead, you may
    /// use this method to access an integer pointer of the structure.
    /// Passing integer versions of this structure is needed because there is no
    /// way to tell the common language runtime that there is extra data at the end of the structure.
    /// </devdoc>
    /// <summary>
    /// Sets the text inside the structure starting from an integer pointer.
    /// </summary>
    /// <param name="pCmdTextInt">The integer pointer to the position where to set the text.</param>
    /// <param name="text">The text to set.</param>
    public static void SetText(IntPtr pCmdTextInt, string text)
    {
        Microsoft.VisualStudio.OLE.Interop.OLECMDTEXT pCmdText = (Microsoft.VisualStudio.OLE.Interop.OLECMDTEXT)Marshal.PtrToStructure(pCmdTextInt, typeof(Microsoft.VisualStudio.OLE.Interop.OLECMDTEXT));
        char[] menuText = text.ToCharArray();

        // Get the offset to the rgsz param.  This is where we will stuff our text
        IntPtr offset = Marshal.OffsetOf(typeof(Microsoft.VisualStudio.OLE.Interop.OLECMDTEXT), "rgwz");
        IntPtr offsetToCwActual = Marshal.OffsetOf(typeof(Microsoft.VisualStudio.OLE.Interop.OLECMDTEXT), "cwActual");

        // The max chars we copy is our string, or one less than the buffer size,
        // since we need a null at the end.
        int maxChars = Math.Min((int)pCmdText.cwBuf - 1, menuText.Length);

        Marshal.Copy(menuText, 0, (IntPtr)((long)pCmdTextInt + (long)offset), maxChars);

        // append a null character
        Marshal.WriteInt16((IntPtr)((long)pCmdTextInt + (long)offset + maxChars * 2), 0);

        // write out the length +1 for the null char
        Marshal.WriteInt32((IntPtr)((long)pCmdTextInt + (long)offsetToCwActual), maxChars + 1);
    }
}