HTML elements using internetexplorer object in vba

Hi I'm trying to access the value at 'data-mod-results-inceptiondate=' within this button object

<button class="o-buttons mod-tearsheet-historical-prices__moreButton mod-ui-
hide-small-below" type="button" data-mod-symbol="GB00B52YRG95:GBX" data-mod-
results-inceptiondate="41043" data-mod-results-startdate="42549">Show more</button>

I can find the button using:

    set btns = IE.Document.getElementsByTagName("button") 
    For each btn in btns
    if btn.innerText = "Show more" then btn.Click
    next btn

How can I find the inner element called 'data-mod-results-inceptiondate' in order to access its value (in this example "41043"). Any help on this would be much appreciated.