>> load_system(myModel);
>> allBlks = find_system(myModel, 'Type', 'block')
Now this will give you all the blocks in the model. So, you can iterate through and find your If block in the cell-array. Lets, say it is the k-th index.
>> allPorts = get_param(allBlks{k}, 'PortConnectivity')
This will have handles for the all the ports. Now, the 1st port is the inport in the If block. You can check the name/block type which is connected to this port.
>> srcBlkType = get_param(allPorts(1).SrcBlock, 'BlockType')
>> srcBlkName = get_param(allPorts(1).SrcBlock, 'Name')
