I am guilty of this too. It is hard. I was also going to say put that money into an account for something. It wouldn't take long before you had more than enough for something for her future or an experience you could all enjoy - Disney World holiday when she is 5 or 6 or earlier if you can't wait that long. We have travelled overseas a few times with our son and I believe it offers him lots of experiences that he wouldn't otherwise have. These may be fun and/or educational but we have also found the concentrated time in our company great for his development.
It is hard but every time you want to buy something write it down and if you really think she *needs* it a few days later buy it then. OR put it on laybuy, not sure if there are fees cancelling it though.
Try cheaper alternatives too - A Toy library allows a big rotation of age appropriate toys for a low outlay. If there is soemthing she *really* loves you could then buy it for birthday etc. Libraries also have a selection of DVDs.
Arrange to do Swimming lessons or other activities on the weekend so you can't go near the shops. Quality time with you is really all she needs.
Hope that helps. Recognising you have a problem is a good start.