Hi there! As a biochemist, I understand your need to plot immunoassay data and produce standard curves using a 4-parameter logistic curve fit. Here's a step-by-step guide on how to do it in Microsoft Excel:

1. First, you need to enter your standard curve data into Excel. This should include the concentration of your standard solutions and their corresponding absorbance or optical density (OD) values. Make sure to label your columns appropriately.
   
2. Once you have your data entered, select the entire dataset and click on the "Insert" tab at the top of the screen. From there, select "Scatter" and choose the scatter plot with smooth lines and markers.
   
3. Next, right-click on one of the data points on the chart and select "Add Trendline". In the "Format Trendline" window that appears, select "Logistic" as the trendline type and make sure the "Set Intercept" and "Display Equation on Chart" boxes are checked.
   
4. Click "Close" to apply the trendline to your chart. You should now see a curved line that fits your data points.
   
5. To read the values of unknown samples from the curve, simply plot their OD values on the same chart and use the trendline equation to calculate their corresponding concentrations. To do this, click on the chart to select it and then click on the "Layout" tab at the top of the screen. From there, select "Trendline" and then "More Trendline Options". In the "Format Trendline" window, check the box next to "Display Equation on Chart". The equation will appear on the chart and you can use it to calculate the concentrations of your unknown samples.

That's it! With these steps, you should be able to plot your immunoassay data and produce standard curves using a 4-parameter logistic curve fit in Microsoft Excel. Let me know if you have any questions or if there's anything else I can help you with.