How to specify the interval between frames in a gif image for a TGIFImage object in c++?

Question

gif

Good day. To create .gif images I use TGIFImage in c++. I can control the speed only through the AnimateSpeed ​​parameter, but it controls the playback speed of the entire GIF. How to make frames duration different? Thank you.
A piece of code for clarity:

TGIFImage *gif = new TGIFImage;
TJPEGImage *jpeg1 = new TJPEGImage();
TJPEGImage *jpeg2 = new TJPEGImage();
jpeg1->LoadFromFile(file1);
jpeg2->LoadFromFile(file2);
gif->Add(jpeg2);
gif->Add(jpeg1);
gif->SaveToFile("GIF.gif");