Switch between different measures on graph formatting

The FORMAT function turns the value into text, so the chart cannot interpret the text in this case.

However, you can change the way the logic works.

You can first prepare 2 series to be used, one for the dollar value and another for the percentage, e.g.
A) myValue = if([Selection3] = 1,0,myTable[ValueToBeUsed]) then set the format from Modeling tab to currency > USD

B) myValue% = if([Selection3]=1,myTable[ValueToBeUsed],0) and keep it unformatted

In the chart series add series A as it is, and add series B as a percent from grand total

When you make a selection to Selection3, the logic of each measure will either show the value or return 0, so only one series will be shown.

You can adjust the percent format from modeling tab to set how many decimal points you want