Using collcell package with tabularx X columntype

I would like to use the X column type from the tabularx with the collcell package.

In the MWE below, I define:

\newcolumntype{R}{>{\collectcell\TitleColumn}{r}<{\endcollectcell}}% works \newcolumntype{T}{>{\collectcell\TitleColumn}{X}<{\endcollectcell}}% fails 

where the T applies the X column type (does not compile and thus is commented out in the MWE) and the R (for illustrative purposes) applies the r column type (which works).

The output has three tables:

1. R column type (to ensure syntax is correct)
2. Desired T column type (commented out)
3. Desired Result of T column type

The error message if table 2 (which uses the T columntype) is uncommented is:

Package array Error: Illegal pream-token (X): `c' used.

Notes:

• MWE is greatly simplified such that there is no need to actually use collcell here, but needed in actual use case where the \TitleColumn and \ColumnL macros have more code.

Code:

\documentclass{article} \usepackage{collcell} \usepackage{tabularx} \usepackage{showframe} \newcommand{\ColumnL}[1]{#1} \newcommand{\TitleColumn}[1]{#1} \newcolumntype{R}{>{\collectcell\TitleColumn}{r}<{\endcollectcell}}% works \newcolumntype{T}{>{\collectcell\TitleColumn}{X}<{\endcollectcell}}% fails \newcommand*{\TabularContent}{% Label 1 Very Long& 62 & 79 \\ Label 2 Empty Row & \\ Label 3 Short& 732 & 31 \\ } \begin{document} \noindent 1. Column type \verb|R| (equivalent to centered \verb |r| column) works fine: \par\smallskip\noindent \begin{tabularx}{\linewidth}{@{}Rll@{}} \TabularContent \end{tabularx} \bigskip \noindent 2. Column type \verb|T| (equivalent to centered \verb |c| column) FAILS \par(commented out): \par\smallskip\noindent %\begin{tabularx}{\linewidth}{@{}Tll@{}}%% <--- How to get this to work % \TabularContent %\end{tabularx} \bigskip \noindent 3. Desired result of above \verb|T| column type is the \verb|X| column type:: \par\smallskip\noindent \begin{tabularx}{\linewidth}{@{}Xll@{}} \TabularContent \end{tabularx} \end{document}