Support for an Excel "Add-In" called EIRT was added in July 2015. This add-in was initially created in 2006 and has been updated regularly since then by its three authors. EIRT has been available on "Source Forge" for some time, where equivalent IRT routines for use with the R language are found in a package called RIRT .
Here's a description from EIRT's Readme.doc file:
This add-in for Excel provide a 'wizard' to estimates the items and
latent variables from the responses of subjects to a
questionnaire. The supported dichotomous IRT (Item Response
Theory) models are the 1PLM (one parameter logistic model), the
2PLM (two parameter logistic model) and the 3PLM (three
parameter logistic model). For polytomous items, Bock's nominal
model, and Samejima's graded model are supported. Two
nonparametric methods (kernel regression an PMMLE) are also
supported. The estimations methods available are the MMLE
(marginal maximum likelihood estimator) and the BME (Bayes
modal estimator, for dichotomous models only) for the
parametric estimation of items, the PMMLE (Penalized MMLE) and
the kernel regression (Nadaraya-Watson) for the nonparametric
estimation of items, and the EAP (expectation a posteriori) and
WMLE (Warm's maximum likelihood estimator) for the latent
From the description, you might sense that English is not the native language of the authors (in fact it's French). You'll get the same impression when running EIRT, but you shouldn't be put off -- EIRT blends in nicely with Lertap 5, and has power.
Read much more about it in this document.